Edwin Jackson’s HR Prevention Against LHBs

At the risk of Edwin Jackson overexposure I wanted to look at one more thing that piqued my curiosity when I was putting together my post last Thursday. Guys who predominately throw sliders and fastballs are typically relievers because of their trouble getting out opposite-handed batters, so I was interested to see how Jackson handles lefties.

His splits are interesting. Although his xFIP shows the split you would expect — 4.63 against RHBs and 5.05 against LHBs — his FIP is actually better against lefties, 4.87 to RHBs versus 4.57 to LHBs. The reason is the big difference in HR/FB rate: 12% against RHBs and 7.5% against LHBs. That is with over 330 innings logged against each. A pitcher’s ability to control his HR/FB is still a pretty open question, and his ability to control HR/FB differentially against lefties and righties even more so. But so far in his career a big part of Jackson’s game against lefties is HR prevention.

Slicing the data any further is dangerous because of sample size issues, but I wanted see whether a specific pitch type was responsible for this difference. So I looked at his HR/FB by handedness and pitch type:

HR/FB
           RHB     LHB   
Fastball  0.153   0.057
Slider    0.100   0.073
Change    0       0.233
Curve     0       0

Remember he very rarely throws anything but his slider and fastball to RHBs, so ignore those last two. And even against LHBs that change is thrown rarely, so put little stock in that number also. The most striking difference, and backed up by the most number of pitches, is the difference off fastballs. A fly ball off his fastball from a LHBs is three times less likely to leave the park than from a righty.

What is going on here? How can he get such a low rate against LHBs and can we expect a rate nearly that low going forward? Here I look at the location of his fastballs to LHBs compared to all RHPs’ fastballs to LHBs. I broke the zone into bins and then color coded the bins. Red indicates zones where Jackson gets a greater fraction of his fastballs, and blues a smaller fraction.

It looks like Jackson hits the middle-away part of the plate pretty well. I think this, coupled with the speed of his fastball, is the key to his HR prevention against LHBs. These blazing fastballs on the outside of the plate are the hardest pitches to pull, and thus get any power off of.