Look at the lines above (stats thru 7/28). They are very similar. Both pitchers are doing a fine job of missing bats with strong strikeout rates. Both are struggling with walks, though pitcher B is much worse off. Both are doing a good job of keeping the ball in the park. And both have been terribly unlucky on balls in play. As you can see by their FIP and xFIP numbers, the walk rate of pitcher B is the biggest difference between these two pitchers. So why is Pitcher B replacing Pitcher A in the 8th inning?
Cleary Pitcher B, David Robertson, is trending up and Pitcher A, Joba Chamberlain, is trending down. With the limited sample size is this really shocking? Is Joba really trending the wrong way or just hitting a rough patch? Almost all middle relievers and non-Mo closers are going to have a few bad outings in a 4 or 5 game stretch that can completely skew the numbers with only 30-40 innings pitched. For Robertson this happened early in the season and for Joba it has happened lately. Is this really a reason to flip their spots in the bullpen? If the intent is to ride Robertson while he’s hot and go back to Joba when he gets in gear I have no problem with it. If it is set in stone however, I can’t agree with the decision.
Even though they have been similar pitchers this year, I think if both are pitching well Joba should be in the 8th inning. Not because he’s necessarily a better pitcher, but I believe he’s more suited for the role. 8th inning guys across baseball have developed, much like closers under Tony LaRussa, into one inning guys who come in with bases empty. While Joba has primarily been a starter in his college, minor league and major league career Robertson has been a reliever thru college and the minors. As a starter Joba opened every inning with the bases empty. Robertson, on the other hand, in his short time in the majors established himself as a guy who can put out fires. In fact, Robertson has faced more batters with runners on than not. Despite his scary walk rates, Robertson does a fine job of pitching with men on base which better suits him for a role in the 7th (or even 6th) inning when runners are on. To make sure this wasn’t just anecdotal; I decided to take a look at Chamberlain and Robertson’s numbers with runners on:
As you can see, both in 2010 and in their career Robertson has been better with runners on. Considering their career OPS’ against are within 1 point of each other it’s a pretty smooth comparison. Joba’s career OPS against with runners on is 13 points worse than with the bases empty. Robertson’s OPS against with runners on is 46 points better than with the bases empty. While Joba doesn’t show much of a difference whether runners are on or not, Robertson clearly pitches better when the bases are occupied.
While Joba hasn’t been great lately, if you told me now the Yankees had a 1 run lead in Game 7 of the World Series (after 7 strong from CC) and needed to choose between Joba and Robertson to come in for the 8th, I’m taking Joba.
For more of my work head over to Mystique and Aura.