Jair Jurrjens: Slower Fastball, Better Results?

Jair Jurrjens is having a great year so far. Obviously, he is getting lucky as he doesn’t have the talent of his league-leading 1.51 ERA. Still, his xFIP of 3.47 is considerably better than his career xFIP of 4.22. This is largely thanks to a big drop in walks, from his career rate of 3.24 to just 1.51 this year. This success is even more striking because his fastball is 1.5 mph slower than he has previously thrown it — usually not a sign of improvement.

Carroll Rogers reported that Jurrjens, 25, picked up a new grip on his two-seam fastball from Jonny Venters, and has been using it since his April 16th start against the Los Angeles Dodgers. But the velocity is down on both his two-seam fastball, from 91.4 mph to 89.4 mph, and his four-seam fastball, from 91.4 mph to 89.7 mph. So I don’t think the change in two-seam grip is responsible for the slower fastballs. He is throwing his two-seam fastball at about the same frequency as he has previously.

Year Two-Seam Fastball Four-Seam Fastball Slider Changeup
2007 36.1% 23.5% 20.1% 20.3%
2008 34.5% 27.0% 11.6% 27.0%
2009 34.1% 27.1% 14.7% 24.2%
2010 32.5% 29.2% 15.7% 22.6%
2011 35.6% 23.5% 17.7% 23.2%

The slower fastballs have resulted in more contact — from a previous rate of 80.9% to 85.6% this year — and thus fewer strikeouts. But he is getting more swings out of the zone and fewer swings in the zone. That leads to more weak contact and fewer walks. It is possible that his slower fastball allows him to better locate just out of the zone to get this out-of-zone swings.

The most striking difference I see is in three-ball counts. Before this year Jurrjens got to three-ball counts in 18% of his batters faced, and then walked the batter in 46% of those at-bats. This year he goes to three balls in 15% of his at-bats. If that were the only difference he would have just a modest drop in walks. But now he walks the batter in just 28% of those three-ball at-bats. Here are the locations of his fastballs to RHBs in three-ball counts in 2010 compared to 2011:

and here to LHBs.

Jurrjens’ three-balls fastballs have been in and around the zone much more in 2011 than 2010 (and other years). This could just be noise, but it might be that with a slower fastball Jurrjens is better able to get the ball in the zone when he needs to.

So, thus far into the season, Jurrjens has succeded partially on BABIP and HR/FB luck, and partially by limiting walks when he gets to three-balls counts. Just because his xFIP has been 3.47 doesn’t mean he will keep it that low, or that he will keep his walk rate that low. But Jurrjens offers an interesting example of a guy who gave up velocity on his fastball and may have improved while doing so.



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Dave Allen's other baseball work can be found at Baseball Analysts.


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