You’ve probably noticed that Joba Chamberlain looks a bit different this season. No, I don’t mean his new mechanics (hands at the waist) or his weight (nyuck nyuck), I’m talking about the way he’s using his pitches. Joba’s scaled back his fastball usage from last year, down to 56% from 65.3%, and is using his curveball exactly twice as often (10.6% after 5.3%). Throwing some more breaking balls is one thing, but it’s when he’s throwing them that’s really interesting.
The graph above, cut right from Joba’s various splits pages on FanGraphs, shows how much he’s used each offering as the first pitch of an at-bat. In his first full season as a reliever in 2010, Chamberlain threw a first pitch fastball more than seven out of ten times. He’s scaled it back a bit this year, instead mixing in some more first pitch sliders and curveballs. Joba’s first pitch strike percentage is essentially the same (58.1% in 2011 after 58.4% in 2010), so he’s not “stealing strikes” with this approach nor is he getting batters to swing at the first pitch more than he did last year (9.7% in 2011 after 11.8% in 2010).
Essentially all Joba has been doing is giving hitters a different look. First pitch offspeed stuff is just a friendly reminder that the pitcher is comfortable throwing any pitch at any time, which makes life that much harder on the hitter*. It’s probably not a coincidence that batters are swinging at 36.6% of the pitches Joba’s thrown them out of the strike zone, the highest rate of his career (it was 35.1% in 2007) and a top 15 mark among all relievers (Mariano Rivera is actually first at 44.2%).
Joba’s ERA is a full run better than it was last season because he’s walking fewer guys (1.85 BB/9 after 2.76) and getting way more ground balls (62.1% after 45.6%) than he did in 2010, making up for a decline in strikeout rate (7.40 K/9 after 9.67). A 17.6% HR/FB ratio is unusually high, so that will correct and help bring his ERA even closer to his 2.80 xFIP. How (or even if) the first pitch breaking balls are contributing to the overall improvement is not something I can definitively say, but Chamberlain’s pitching sequences and overall performance have been noticeably different.
* I remember hearing Al Leiter say that he threw a curveball on the first pitch of Game Seven of the 1997 World Series for that very reason, to show the Indians that he was going to make them guess all game long.