Comparing the bullpens of Boston and New York

There’s a lot to dislike about the Rafael Soriano signing: the loss of a draft pick, the injury risk, the salary and the fact that Sergio Mitre is still the fifth starter. However, there’s one thing to be very happy about, and that’s how strong the Yankee bullpen figures to be.  Last summer at TheYankeeU I spent a fair amount of time using Baseball Prospectus’ Tommy Bennett’s methodology on reliever dominance.  Bennett’s jumping off point is trying to understand and evaluate Mariano Rivera; even advanced metrics can’t consistently rate Rivera accurately.  This is because he has the relatively unique ability to sustain a consistently low BABIP and prevent home runs.  Stats like FIP and xFIP would then prove relatively useless to analyze Rivera.  For instance, take a look at Rivera’s Fangraphs page.  His ERA has been below his FIP and xFIP virtually every year of his career.  Anyone care to predict that this year will be different? Bueller?

So Bennett tried out a different methodology to evaluate reliever skill based on two stats: SIERA and WXRL.  He described them in an earlier piece accordingly:

The gist is [SIERA] gives an estimation of a pitcher’s controllable skills (fly ball rate, strikeout rate, ground ball rate, and walk rate) and considers how they interact with one another. Put simply, it’s a way to evaluate the totality of a pitcher’s skills while looking beyond contingent (or luck-based) factors.

WXRL, on the other hand, is a metric based on win expectancy. It simply measures, compared to replacement and adjusted for quality of opposing lineup, how the likelihood of the reliever’s team winning changed from when he entered the game to when he left.

This is simple enough.  The next step Bennett took was to calculate a Reliever Score based on the two stats.  The methodology sounds complicated but is relatively straightforward.  Cue Bennett again:

We’ll take WXRL and SIERA for all pitchers who have pitched solely in relief. For each pitcher, we’ll calculate how many standard deviations they are away from the mean in each category. Then we’ll add them together. For example, a pitcher who was one standard deviation better than the mean in both SIERA and WXRL would get a score of two.

For our purposes I’ve set slightly different parameters.  I set the cutoffs at 20 innings for relievers only, used data from the 2010 season, and then pulled out the relievers on Boston and New York.  The results for Boston are first.  Keep in mind that a higher number with WXRL is better (based on Win Expectancy), and that SIERA is like FIP, so it’s scaled and comparable to ERA.

Daniel Bard registered the highest Reliever Score in the Boston bullpen based on a very high WXRL score in 2010.  This is hardly surprising; Bard is an elite pitcher with an incredible arsenal who often found himself in high leverage spots for the Red Sox last season.  One interesting aspect to the chart is seeing Bobby Jenks grade out better than Papelbon in SIERA.  Boston earned accolades from the stat community for their signing of Jenks, and rightfully so. Jenks’ SIERA score is sending the same message that his FIP sends – that his peripherals were intact and that a bounceback wouldn’t be unexpected.  Jenks registers a low WXRL, but that’s not surprising given his poor results in 2010; if his BABIP normalizes and he’s used in high leverage spots this number ought to increase in 2011.  All told the most interesting aspect of this chart is that Jenks scores the best among any Boston reliever in K/BB ratio and SIERA.  If he is able to recover and have a better 2011 it’ll really help out Boston’s middle relief and make his contract look like a steal.

One area of weakness is the lefty reliever.  Doubront appears headed back to AAA this season, leaving only Hideki Okajima coming from the left side.  Okajima’s numbers are some of the worst of any reliever on this list.  He’s historically tough on lefties (3.50 K/BB ratio, 0.591 OPS against), so he could have greater value in 2011 if used more sparingly.  Now to the Yankees:

Here we see the strength and depth of the Yankee bullpen.  Simply put, Rivera and Soriano are a two-headed monster.  It wouldn’t be a surprise for Soriano’s BABIP and HR/FB ratio to rise in 2011, especially in Yankee Stadium behind the Yankee defense, but he’s always been a strikeout-heavy pitcher equally adept at limiting free passes.  It’s also notable how well Joba Chamberlain looks.  A lot of fans love the idea of Joba the starter, and for good reason, but Joba the reliever is probably underrated at this point.  Much like Bobby Jenks, Joba’s advanced stats and peripherals make him look far better than his ERA would indicate.  In fact, as Moshe from TYU noted, he looks very similar to Daniel Bard’s statistical profile, and their respective SIERA numbers back this up:

And yet, the numbers show that Joba was about as good as Bard was last season, and that with a little bit of luck, the perception about him would likely be vastly different. Furthermore, Bard is actually 3 months older than Chamberlain, a fact that would surprise most but suggests that they are on equal footing in terms of development. I do not mean to suggest that Joba was actually better than Bard in 2010, as there is something to be said for ERA and results, such that I would not explain all of Joba’s struggles away using the “luck” factor. But the peripherals clearly tell us that these two pitchers should be regarded similarly, and I would be far from shocked if Joba and Bard put forth extremely similar seasons in 2011.

Alongside Joba in middle-to-late relief is David Robertson, the forgotten cog in the bullpen wheel.  Both of these relievers are probably capable of manning the eighth inning, so hopefully they’ll be able to prove themselves in high leverage spots this season.  It’s almost an embarrassment of riches, to be frank, and really underscores the fact that the Yankees could extract more value from Joba as a starter than as a reliever.  The Yankees also figure have two solid lefties this season.  Given the strength of the Soriano, Chamberlain and Robertson, it stands to reason that Feliciano can be used more sparingly than he has been in the past, deployed particularly against lefties.  Get ready for long games full of pitching changes and endless unfunny binder jokes.

At great cost the Yankee front office (and ownership!) has assembled a very good bullpen this winter.  If they’re able to acquire another starting pitcher and/or persuade Andy Pettitte to return then the staff on the whole figures to be very solid.  It’s also pretty safe to say that this bullpen looks better on paper than Boston’s heading into this year, and may in fact be the best in baseball.  The Yankees have missed out on a lot this offseason, but the bullpen is very respectable.  Hey, it’s the little things.