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The David Robertson – Mark Wohlers comparison

The 2009 Yankees featured an excellent bullpen, and a big part of that came from the success of David Robertson. A 17th round pick in 2006 out of the University of Alabama, Robertson dominated the minor leagues and forced his way onto the major league roster just two years after turning pro. He had some hiccups during his 30-inning cup of coffee in 2008, but came back strong in 2009 to earn a regular spot in the bullpen.

We saw plenty of good from Robertson, jokingly nicknamed K-Rob, in 2009. His strikeout rate, 13.0, ranked second among major league pitchers with at least 40 innings. Using his fastball, which traveled a mile per hour faster than in 2008, he blew away hitters. According to FanGraphs pitch type values, Robertson’s fastball measured 4.7 runs above average, or 0.73 runs above average per 100 pitches. His curveball provides another weapon, as he can drop it as a change of pace. We saw more than one hitter’s knees buckle on a K-Rob hammer in 2009.

When examining the Yankees bullpen, I lumped Robertson in with the presumed bridge to Mariano, along with Joba/Hughes and Marte. Given the way he pitched in 2009 we can expect that he’ll get every shot to pitch in high leverage situations. But one thing remains troubling about Robertson: his walk rate. This has been an issue for him throughout his baseball career, dating back to his days as closer for Alabama. His strikeouts help cover it up, but his walk rates, typically in the mid-4s, are too high almost every year. Is this something he can correct in the future?

Certainly the possibility exists that Robertson can improve his walk rate. In fact, a similar pitcher with a familiar face did just that almost 15 years ago. From 1992 through 1994 Mark Wohlers pitched 134 big league innings and walked over 4.5 hitters per nine innings. Robertson doesn’t have that much experience — he didn’t hit the majors until 23 — but his walk rate hovers around that area. Wohlers compensated for the plentiful walks by striking out a ton of hitters, reaching 10.2 per nine by 1994, and allowing few home runs, just three in those 134 innings. Robertson, by comparison, has struck out 99 hitters in his 74 big league innings while walking 38 and allowing 7 home runs.

The good news for Robertson is that in 1995, when Wohlers turned 25, the same age Robertson will be for the 2010 season, he reduced his walk rate to 3.3 per nine, while raising his strikeout rate to a K-Robian 12.5 per nine. This resulted in a 2.09 ERA and his installation as the Braves closer. Wohlers continued the trend in 1996, lowering his walk rate even lower, to a downright awesome 2.4 per nine. The next year, however, the walk rate crept back up, and after that Wohlers was never the same.

The case of Mark Wohlers shows us that yes, Robertson can correct his walk tendencies. Wohlers not only did it, but did it at the same age as Robertson. True, Wohlers burnt out young, his last effective season coming at age 27, but given the general volatility of relievers I think the Yankees would be more than glad to get three year of Wohlerian performances out of Robertson, even if it means his flaming out early.

We really don’t know, however, if Robertson will make the correction. He can still be a useful cog if he continues to walk hitters at his current clip. But he’ll be a much better fit for the late innings if he throws more pitches in the zone, or otherwise gets hitters to swing at more pitches out of the zone. That much is obvious. What I’ll be looking at in the 2010 season is of the actual adjustments he makes. Clearly he’s a talented pitcher. Maybe everything will come together for him at age 25.

Credit: AP Photo/Matt Slocum

Yanks bring aboard Segovia as a non-roster invitee

This isn’t breaking news, but we’ve yet to address it here. The Yankees have invited righty reliever Zack Segovia to Spring Training as a non-roster player. He’s appeared in just nine big league games over the last three years, and even his minor league numbers aren’t all that impressive. There’s no harm in inviting a guy to ST, and if anything he’ll be someone Triple-A Scranton manager Dave Miley could run out there every day to take the pressure off the younger arms in the bullpen.

Yep, it’s that kind of morning.

When the Yanks traded Roberto Kelly

It’s hard to believe that 2009 marked the first time since Paul O’Neill patrolled right field that the Yanks won a World Series. Since the era of O’Neill, the Yanks tried a variety of players in right. Raul Mondesi got his crack, and Gary Sheffield and Bobby Abreu held down the three-hole in the lineup for a few years. Now, the spot is Nick Swisher‘s for the foreseeable future, and we fondly remember O’Neill.

It wasn’t always like that though. When Paul O’Neill first arrived in the Bronx, fans and commentators responded skeptically. He was some overhyped 29-year-old from Cincinnati who was more known for his temper than for his bat. He could never hit as well as he was supposed to, and the Yanks gave up a one-time untouchable player to get him.

The trade come down on November 3, 1992. The Yankees, a few weeks removed from a fourth place, 76-86 finish, were looking for a big lefty bat, and the team needed some pitching too. So they traded Roberto Kelly for Paul O’Neill. At the time, media coverage focused around what the Yanks gave up rather than what they got back. “The Yankees,” Jack Curry wrote, “scrapped their glorious plans involving Roberto Kelly yesterday and traded their once-untouchable outfielder to the Cincinnati Reds for power-hitting right fielder Paul O’Neill.” Kelly was “someone they would not trade because of his potential to be their next superstar.”

In O’Neill, the Yanks had potential, but Murray Chass wondered if they had anything else. Chass saw the troubles and the way Steinbrenner would grate on O’Neill. He didn’t know if the temperamental lefty could survive the wrath of the Boss after suffering through Lou Piniella while with the Reds.

Meanwhile, with Paul in the fold, speculation about the Yanks’ impending moves grew louder and louder. Curry wondered if the team would pursue Barry Bonds, and David Cone, Jim Abbott and Greg Swindell were rumored to be on the team’s wishlist as well. My, how times have changed.

In the end, the Yanks were the clear winners of that trade. O’Neill played 1254 games in the Bronx over the next nine years, and his arrival signaled the start of a smarter approach to team-building. Playing next to Bernie Williams and hitting in front of him, O’Neill went on to put up a .303/.377/.492 with 185 home runs in the Bronx, and outside of an ill-fated two-week stint by LaTroy Hawkins, no one has worn 21 since he did. As for Roberto Kelly, he wasn’t as lucky. The one-time future superstar played just 699 over the last few years of his career and hit .299/.342/.446. He retired after a short return to the Bronx in 2000 and now serves as the first base coach for the Giants.

In 1992, the Yankees took a chance on a 29-year-old, and only the water coolers lived to regret it.

Photo Credit: AP Photo/Jeff Zelevansky

Open Thread: Uniform numbers and nothing else

Every one in a while I run across one of those “on this date in history” items that involves the Yankees. As I traipsed around the internet today, I ran across a pretty significant one. On January 21, 1920, the Yankees announced that their players would wear uniform numbers. No other team in baseball did this at the time. Instead of letting players pick, they had numbers assigned based on batting order position. Hence, Babe Ruth got 3, and Lou Gehrig eventually got 4.

While the format for handing out numbers changed — players choose now — I’m glad nothing else did. It’s kind of neat that the Yankees don’t have their names on the backs of their jerseys. It’s also good for fans, who can buy one overpriced authentic jersey and wear it through multiple players. It worked out real well for those who bought Jason Giambi jerseys. Not so much, though, for people like my buddy Jon who bought a Sheffield jersey.

Oh, and just because we haven’t yet mentioned it, the Pirates DFA’d former Yankee Anthony Claggett to make room for former Yankee Octavio Dotel. Claggett is the second former Yankee the Pirates have DFA’d this week. Steven Jackson is the other. They released Eric Hacker in November, and he has since signed a minor league deal with the Giants.

In local sports, the Rangers visit Philly and the Panthers face the Islanders. No local basketball, though NBA fans will probably want to watch the Lakers at Caveliers at 8 on TNT. Big East basketball fans can catch Seton Hall at Louisville on ESPN or ESPN2.

And now, your open thread.

Minor Notes: Montero, Vizcaino

Got a few minor league nuggets worth passing along this afternoon, so let’s get to it…

  • John Sickels at Minor League Ball posted some excerpts of player write-ups from his book today, and Jesus Montero was one of the lucky few. You might fool him once,” says Sickels, “but don’t try the same trick too soon or he’ll make you pay. I have absolutely no doubts about Montero’s bat.”
  • Meanwhile, the crew at Project Prospect posted their list of the ten best prospects in the game, and Montero checks in at number three. Jason Heyward tops the list, and is followed by Desmond Jennings of the Rays. Montero is one spot ahead of Stephen Strasburg, who I consider to be the very best prospect in the game. Either way, this is elite company we’re talking here.
  • Last, but certainly not least, Kevin Goldstein released his top eleven Braves’ prospects today. Former Yankee farmhand Arodys Vizcaino ranks third behind Heyward and Julio Teheran. Somehow he managed to go from a four star prospect with the Yanks to a five star prospect with the Braves in less than a month. Go figure.

The stats we use: wOBA

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)