The stats we use: wOBA

Javy Vazquez: The new Andy Pettitte?
Minor Notes: Montero, Vizcaino

Just because people term a statistic “advanced” doesn’t mean it requires an overly complex calculation. Last week we examined UZR, and that might have given off the wrong impression. UZR is complex out of necessity. A baseball field contains 78 zones, and to calculate defense we must account for multiple zones per player. This involves not only balls hit into the zones, but also the type of ball hit into the zones and the rate at which other players converted those balls into outs. Offensive statistics, however, are a bit more straight forward. It helps, too, that we’re already familiar with the components.

This week we’re going to dive into weighted on base average, or wOBA. Developed by Tom Tango, the stat attempts to reconcile OBP and SLG, two of the most important offensive statistics. They both measure one thing while ignoring others. OBP measures how many times a player reaches base while ignoring the difference between a walk and a home run. SLG measures total bases while ignoring walks. wOBA weighs both and combines them for an offensive statistic that more accurately represents a player’s value.

What about OPS?

At this point you might be saying, “But they already have OPS. That combines OBP and SLG. So what gives?” True, OPS stands for on-base plus slugging, so why the need for a more advanced calculation? The answer deals with the scales upon which each metric is based.

The denominator in OBP is plate appearances, while the denominator in SLG is at-bats. True, they’re expressed in decimal format, and that might make it easier to slap them together. That doesn’t mean it is correct. Beyond the denominator issue, we also have an issue of scale. OBP is almost always going to be lower than SLG, because OBP is binary. You either reached base or you didn’t, meaning you get a 1 if you succeed and a 0 if you fail. SLG, on the other hand, measures total bases, so a player receives 4 for a home run, 3 for a triple, 2 for a double, and 1 for a single. And, again, it works with a smaller denominator, since at-bats is a subset of plate appearances.

By merely adding together OBP and SLG, we get a number that greatly favors power hitters. High on base guys will still climb the OPS charts, but their lack of power will keep them away from the top. What we want an on-base plus slugging stat to accomplish is to properly weigh these two aspects and provide us a proper valuation of offensive contribution.

How do we weigh events?

Instead of working with OBP and SLG, Tango decided to start from scratch with wOBA. This makes perfect sense. Statistics are just a recording of what happened on the field. OBP examines walks, hits, and outs. SLG examines singles and extra base hits. Why take those two pre-made calculations when the available data allows you to weigh the individual components of these stats before their OBP and SLG calculations? That’s exactly what Tango did.

In last week’s UZR primer, we looked at linear run estimators, which assigns a certain run value to each offensive event. This comes into play again for wOBA. After breaking offense down into its individual components, we can then weigh the value of those components and combine them for a rate stat. With wOBA, however, we’re looking at the runs above the run value of an out, which is zero in an OBP calculation. So here’s an updated linear run estimator, in terms of runs above the value of an out.

Event Value
Single 0.77
Double 1.08
Triple 1.37
Home run 1.70
Walk 0.62

The only step left is to scale the stat to OBP. This isn’t necessary — in fact, the league-average hitter under this situation would be around .300, which seems like a neat, round number. But, since we’re talking about a weighted OBP, Tango decided to scale it so the league average is around .340. That requires adding 15 percent to each weight. Again, not a big deal. It just makes the end result easier to understand.

Stolen bases

Yes, wOBA includes stolen bases. Successful stolen bases weigh at 0.20, while a caught stealing around -0.44. Tango provides a full list of linear weight events here.

Runs above average

Using wOBA, we can easily determine how many runs above average a player contributed. All we have to do is subtract the league-average wOBA from the player’s wOBA. But, because of the 15 percent weight added for scale, we need to divide by 1.15 to strip that out.

No adjustments?

No, there is no wOBA adjustment for park, position, or league. Individuals can make these calculations, but wOBA is meant as a context-neutral stat. Again, just as OPB and SLG are not park adjusted, nor is wOBA.

What about OPS+?

On Big League Stew, Alex Remington is running his own series of articles on advanced statistics. I try not to use what he writes in mine, especially because we’re trying for different purposes. In his wOBA primer he makes a statement with which Tango takes issue. Alex says that wOBA is “superior to non-weighted stats like OPS and OPS+.” The statement is inaccurate, because OPS+ is weighted. But, as Tango notes, it is weighted improperly.

Sean Forman, proprietor of Baseball Reference, leads the charge with OPS+. He essentially weighs OBP to SLG at a 1.2 to 1 ratio. That appears to improperly undervalue OBP, and Tango argues that the ratio should be more like 1.7 or 1.8 to 1. Because OPS+ does park and league adjust, that would make OPS+, as he says, “(almost always) superior to wOBA.” Again, this comes from the man who created wOBA.

To remember

Unlike all-in-one stats like WAR and WARP3, wOBA doesn’t try to tell us everything. What it does try to tell us is the value of a player’s offensive contribution. It doesn’t necessarily favor guys who walk a lot, like OBP, or guys who hit for a lot of power, like SLG and OPS. It breaks down offense into its core events, weighs those events, and then adds up the value. It also adjusts to a familiar scale, making it easier for us to understand, at a glance, the value of a player’s contribution.


wOBA from The Book
Getting to know wOBA
The history of wOBA, part 1 (to which there seems to be no part 2)

Javy Vazquez: The new Andy Pettitte?
Minor Notes: Montero, Vizcaino
  • pete

    I <3 RAB

    • tommiesmithjohncarlos a/k/a Archimedes Torquemada

      RAB’s career wOBA is like .517. Astronomical. Bondsian, even.

      • pete

        I knew RAB was juicing. Too good to be true.

        • tommiesmithjohncarlos a/k/a Archimedes Torquemada

          It was a loosey goosey era.

          • Rocky Road Redemption (formerly RAB poster)

            Well, they claim they haven’t been juicing. They’re going to gather more information then get back to us.

            They really wish they’d been born in a different era, though.

          • Steve H

            Their cousins told them to take it, so they did.

          • Thomas

            Steroids didn’t help them write better. It just kept them healthy.

  • AeroFANatic

    Edited by RAB: Completely off-topic

    • Rocky Road Redemption (formerly RAB poster)

      Heh. I’m laughing a bit meanly because my ultra-mega-super off topic post from the previous thread has still not been deleted. And, if I’m being honest with myself, it should be.

  • tommiesmithjohncarlos a/k/a Archimedes Torquemada

    Because OPS+ does park and league adjust, that would make OPS+, as he says, “(almost always) superior to wOBA.” Again, this comes from the man who created wOBA.

    Isn’t that the point of wRC+?

    To make a park and league adjusted central offensive production stat that is centered around the linear weight model of wOBA, rather than the cruder OBP and SLG-centric model of OPS?

    So, wRC+ >>> OPS+ >>> wOBA >>> OPS >>> SLG and OBP >>> BA?

    • Joseph Pawlikowski

      Might be. I haven’t read up too much on wRC or wRC+ yet, but you can be sure they’ll be part of this series.

      • tommiesmithjohncarlos a/k/a Archimedes Torquemada

        I just did what they call in the television broadcasting industry a “teaser”.

        You’re welcome.

        • Mattingly’s Love Child

          And if RAB had an app for my Blackberry, I would definitely not miss out on those parts of the series!

          I’ll just have to be extra attentive for the next couple of weeks.

          • tommiesmithjohncarlos a/k/a Archimedes Torquemada

            During Sweeps Week, Riddering and Optimist Prime are going to have a jello bikini fight.

            • Tampa Yankee
              • Tampa Yankee

                safe btw

                • Steve H

                  I was going to click, then you told me it was safe.

                • tommiesmithjohncarlos a/k/a Archimedes Torquemada

                  The ol’ “baby on the corner” trick, eh?

                  Not gonna fall for that shit.

                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  hey! baby! what’re you doing out on the street, it’s not safe out there!

        • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

          leno would like to speak to you

          • tommiesmithjohncarlos a/k/a Archimedes Torquemada

            NBC: Nothing but co#$%uckers

            • Drew

              Sandler ftw

            • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

              nah he didnt say suckers. he said either cu%^$ or co@&$

              id like to know whether it was male or female anatomy

              • tommiesmithjohncarlos a/k/a Archimedes Torquemada

                I’ll guess, based on rudimentary lip reading, it was female.

            • Januz

              Actually NBC Stands for NOTHING BUT CELLAR. For example, they had ratings last summer that were the lowest since the 1950s. They have managed to make Law & Order suck, and have not come up with a decent show on the network in years. The ratings on MSNBC are hopeless, and Universal Pictures was only behind MGM in box office receipts. The only things I watch on NBC are football, golf & hockey, and on USA Network: White Collar: What a real comedown from the days of The Cosby Show.

              • tommiesmithjohncarlos a/k/a Archimedes Torquemada

                I now know how Januz feels about this.

                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  oldie but goodie

                  and burn notice starts tonight, great show on usa, and psych starts this wednesday, great show on usa. and royal pains comes back at some point, great show on usa

                • king of fruitless hypotheticals

                  whatever happened to dirty sexy money?

                  nip/tuck, archer, house.

                • Januz

                  Those shows are not bad. But they are not programming I would go crazy for. The only new show to come on network TV that is newer than 5 years old, and is really good is “Castle”. I like “White Collar” but not like “Castle”. NBC also promotes shows like “Chuck” like it is Mission Impossible or worse, James Bond, despite the fact it is not even as good as “Alias”.

                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  whatever happened to dirty sexy money?

                  nip/tuck, archer, house.

                  none of these are on nbc

                • RL

                  I’ll take Dirty Sexy Money over Castle any day. Castle is too predictable.

                • tommiesmithjohncarlos a/k/a Archimedes Torquemada

                  none of these are on nbc

                  Januz was speaking of the wider, overarching NBC/Universal family of networks and entertainment outlets, therefore, the shows on USA Networks (an NBC sister station) were included in the discussion.

                  I know it was confusing to follow, so I understand how you got off track. If only there would have been some nested parentheticals to help guide you on your way…

                • Januz

                  You are correct I should have mentioned that USA, Universal, MCNBC etc are part of the GE/NBC Family (Soon to be Comcast). The point about NBC is their programming is not only bad, but it is far befind the times, and is not going to build a new audience: Law & Order, Leno, Springer & Maury (Universal Owned shows) all stuff from the NINETIES or earlier.

          • Mattingly’s Love Child

            You had such a simple tag for so long…damn man what happened?

            • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

              don’t worry, once tatis signes somewhere itll go away cause i cant officially endorse his signing anymore

              • tommiesmithjohncarlos a/k/a Archimedes Torquemada

                And Coco will probably be at Fox come September.

                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  this will not end well

                • tommiesmithjohncarlos a/k/a Archimedes Torquemada

                  For NBC, no, probably not.

                  The question is, does Conan stay in LA or go back to NYC? Does he want to compete for guests head-to-head against Letterman, or Leno?

                  The smart move would probably be to stay in LA and ride the anti-Leno wave as long as possible, but Conan’s an east coast kinda guy. I bet he comes back.

                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  i just cant see a show like that being successufl on fox. esp since they make bank on syndicated reruns from 11-12

                • tommiesmithjohncarlos a/k/a Archimedes Torquemada

                  I agree. Fox isn’t even a real network yet, since they don’t show original programming during the 10pm hour.

                  But, they’ll probably make a play for Conan, he’s the best hope they’ve ever had for getting into the late-night hour. At 11:00, he can challenge the late news broadcasts and probably win.

                  He’ll have a shitty lead in, though.

                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  how much would youlove to see them push the news to 11 and have conan at 1130. leno letterman and conan all against eachother would be amazing

                • tommiesmithjohncarlos a/k/a Archimedes Torquemada

                  I’d love it, but Fox can’t afford to do all that in this economy. It’ll cost a buttload to get up and running with 5 nights of 10pm programming by September.

                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  nah, reality tv. boom. bring back hells kitchen, that way, at 10 the guy can be much meaner and more abrasive and maybe they can throw in some suggestive behavior

                • tommiesmithjohncarlos a/k/a Archimedes Torquemada


                  Just seems like that switch is a damn complex one to make. You also have to deal with all your affiliates moving their news broadcasts back an hour (and shortening them by half). Not sure what the revenue implications of that is, but I’m sure it’s not inconsequential.

                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  true..but one would think that you could make a lot more on an extra half hour of non news than you can on an hour no? i mean, they have news for 2 hours from 5-7 and there isnt that much happening locally to fill an hr from 10-11 anyway, most of it is fluff crap anyways and probably loses viewers after the first 15 mins and gets them back for the last 10 for sports and weather (conjecture on my part)

    • pete

      “So, wRC+ >>> OPS+ >>> wOBA >>> OPS >>> SLG and OBP >>> BA?”

      I think that’s a fair assessment, yes.

      What I think is interesting is that when it comes to evaluating prospects and minor leaguers, you’d probably be more inclined to go with something like this, where you’re depending more on raw talent that’s likely to exceed at the next level than pure win-related results evaluation:


      • pete

        or would you put OPS+ above wRC+? I suppose you probably would.

      • tommiesmithjohncarlos a/k/a Archimedes Torquemada

        Meh, it’s more a division between simple, all-in-one stats to compare players amongst their peer groups vs. separate, individual stats to drill down into a single player’s ability to forecast and indentify strengths and weaknesses.

        wOBA and wRC+ are great stats for, say, deciding who to be interested in (or not interested in) amongst 5-10 players on a free agent market, i.e. is Marlon Byrd’s total production worth more or less than Gary Sheffield’s, or are both of them better than/worse than the in-house options we have.

        It’s not the best tool for evaluating minor leaguers, though, because you’re not really interested in comparing Austin Jackson to Curtis Granderson. You’re more interested in what Austin Jackson is AND who he’ll become, and for that level of forecasting you need all the dozens of individual component metrics that go into the big super-stats like wOBA. wOBA is too all-encompassing to notice individual trendlines in things like K/9 or GB/FB or Swing Percentage or stuff like that.

        • pete

          well yeah I would certainly agree. I was just ranking how much somebody would care about the listed statistics in a minor league or prospect evaluation setting. For me, for a hitter, I’d probably rank them like this:

          LD%>SLG>K%> anything else

  • Mattingly’s Love Child

    RAB = The bees knees

    Thank you guys for this. Sometimes going to Fangraphs is really overwhelming to understand all of these statistics, especially for a idiot like me. I feel I have a much better understanding of wOBA now. The true test is if I can explain it to my 62 year old father while we’re watching games in April.

    • Mike Pop

      “The true test is if I can explain it to my 62 year old father”

      good luck with that.

      • tommiesmithjohncarlos a/k/a Archimedes Torquemada

        Print out this page, and bring it with you to the ballpark.

      • Mattingly’s Love Child

        Well he bought into UZR because for years he thought Jeter’s defense was over-rated, but had no proof other than his eyes.

        And I used Pujols and ARod vs Ted Williams to explain OPS, and what is a good OPS.

        So I’ll have to find a way to tie it into specific players…

        • A.D.

          Something with a good base-stealer to show his value?

          • Mattingly’s Love Child


  • Chris

    Tango provides a full list of linear weight events here.

    Does wOBA consider all of the other events listed, such as reached on error HBP, etc?

  • pete

    One thing i wonder is that why, since wOBA is context-neutral (and anyone in their right mind would look at wRC+ over wOBA when evaluating a player), does it bother with the linear weights? That is not to say that I don’t appreciate the creation of weighted statistics, but if you’re weighting them, then what’s the point of keeping it context-neutral?

    I guess what I’m saying is that while it’s much more useful when it comes to player evaluation at the FO level, I think it would be cool to have a completely neutral combination stat. One where, for example, a walk = a single = a HBP = a SB, etc. In other words, one that simply counts how many bases a player takes minus how many extra outs he makes, against total plate appearances. The formula would look something like this:

    (TB + BB + HBP + SB – CS – GIDP) / TPA

    The reason I bring this up is because I worry that the linear weights could be affected by sample. For example, the weight of a single could be quite accurate, but a HBP not as accurate because there are fewer, and therefore the comparative relationship breaks down, breaking down the whole weight system to begin with. Plus it’d be kinda cool to see exactly how many bases a player was worth without the run/win relationship context. At least I think it would.

    • pete

      well just read in the comments of tango’s list of weights that the data comes from 1959-2009, so i’m guessing there’s not much of a SSS issue. so scratch that. I still think it’d be interesting to see the raw numbers though, and especially interesting to see how they stack against wOBA

    • Januz

      There are too many stats and regression analysis techniques being used in baseball. These techniques are what are used against Jack Morris when Hall Of Fame discussions come up. What matters to me is playoff and World Series type situations, not August against the Royals. I have seen enough of Andy Petitte down through the years to understand what this means. He rarely has superior stuff, but he manages to get through and win (Such as in the 2009 World Series).

      • tommiesmithjohncarlos a/k/a Archimedes Torquemada

        All of what you just said: batshit insane.

        • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

          can i unread what januz thinks?

          • Steve H

            Heh. I’m the exact opposite. I re-read it about 5 times so far, seriously.

      • Steve H

        Nope. Jack Morris’ ERA of 3.90, while not a great statistic, is more than enough to keep Jack Morris out of the Hall. You don’t even need to dig any further, though I will admit, digging further pushes Morris away from the Coop even more.

        Oh, and Pettitte the regular season pitcher=Pettitte postseason pitcher.

      • Steve H

        Ted Williams postseason: .200/.333/.200. 0 HR’s, 1 RBI.

        Ted Williams, not in Januz’ Hall of Fame.

        • tommiesmithjohncarlos a/k/a Archimedes Torquemada

          I bet Ted Williams would have MURDERED the Royals in August, though, had the Royals existed during his day.

        • Januz

          Williams’s post-season numbers were very small (Only appearing in one World Series). So you can’t use that. Look at Dave Winfield’s 1981 World Series, and you will see an example of a player who is better in May than October. Morris is a Hall of Famer, Andy is not, but Ansy’d performances in big games is well above average (See Game 5 1996 World Series).

          • tommiesmithjohncarlos a/k/a Archimedes Torquemada

            Morris is a Hall of Famer, Andy is not,

            Jack Morris and Andy Pettitte: Two guys who should pay admission to get into the Hall of Fame, just like you and me.

            • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)


              • tommiesmithjohncarlos a/k/a Archimedes Torquemada



                • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

                  what’re you gay?

                  \iron horse’d

          • Steve H

            So is Dave Winfield NOT a HOF in your eyes?

            • tommiesmithjohncarlos a/k/a Archimedes Torquemada

              This will end badly.

          • Steve H

            So you want to talk about Williams small postseason appearences for his numbers, then bring up ONE game Pettitte pitched. Again, Pettitte is the same pitcher in the regular season as the postseason. You want to bring up 1 Pettitte performance in a big game? I’ll bring up another. 2001 WS, Game 6. Could have clinched the WS, and what did he do?

            2 innings, 6 runs. Way to go “big game Andy”

            • jsbrendog officially approves signing Fernando Tatis (and is with CoCo)

              but he saw ’96 with his own eyes

      • Rocky Road Redemption (formerly RAB poster)

        [Golf clap]

        This is up there with the LoHud article.

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