The Starting Pitcher Strikeout Rate Decline Candidates

Yesterday, I took the first look of the 2015 season at starting pitcher’s xK%. I began with the potential surgers, those pitchers whose expected strikeout rates were most above their actual marks. Today will be the opposite side of the coin. These pitchers have posted strikeout rates significantly above what their mix of strike percentage, swinging, called and foul strike rates suggest. They could be in for strikeout rate collapses if they don’t improve those peripherals.

Mark Buehrle is fun. Thought a career low 9.4% strikeout rate was sure to rise? His xK% laughs at that notion. His swinging strike rate is third lowest in baseball, which combines with the third lowest called strike rate. Perhaps his days of SIERA outperformance are finally over.

Jon Lester outperformed his xK% last year as well, but to a relatively minor degree. Going back to 2008 (all the data I have), he has underperformed his xK% just twice, outperformed four times and was about in line once. So perhaps the formula is missing something. But still, this disparity has to narrow. But with a 6.23 ERA as a result of a ridiculous .424 BABIP, he’s obviously not sell high candidate. I just wouldn’t expect his SIERA to remain below 3.00.

Clayton Kershaw has a 34.3% strikeout rate and his ERA sits above 4.00! WHAAAAAAAAAAAAAAAAAAAAT?!?! And check out that 28.1% line drive rate and .393 BABIP! Kershaw allowing hard contact?

I was too nervous to roster Phil Hughes because it relied on him repeating his absolutely elite control. Sure enough, his strike percentage has remained above 70% and his walk rate below 2%. The only difference between these two seasons has been his HR/FB rate. Last year he was extremely fortunate, and this year the pendulum has swung in the opposite direction. This is precisely what we mean when we talk about the luck element of the HR/FB ratio. Unfortunately, he’s not fooling anyone this year as his swinging strike rate has plummeted.

Wow, what happened to Wily Peralta? You thought an 11% K% was terribly disappointing?! Perhaps it should be worse! His fastball velocity is down two miles per hour, which is concerning. But interestingly, his swinging strike rate has only declined marginally from last year. What has killed him is the second lowest looking strike rate in baseball and a relatively low rate of foul strikes. He was a bottom tier option in mixed leagues to begin with, so I’m not particularly interested in holding him to see if he turns things around.

I think any Clay Buchholz will take even that xK% mark! His excellent last outing makes it more difficult to buy low, but he’s looking like a major rebound candidate.

I have been a big James Paxton fan given his big velocity, ground ball tendency, excellent curve and solid change-up. This year, both of those secondary pitches have continued to induce a high rate of swings and misses. But his fastball has been poor and the velocity on the pitch is down. For whatever reason, his foul strikes have disappeared, which is probably a bit fluky. But you would expect that a pitcher with his stuff would induce more swings and misses. Maybe he should mix in his off-speed stuff more frequently and throw his fastball less than two-thirds of the time.

Johnny Cueto outperformed his xK% last year as well, though to a lesser degree, but prior to that his strikeout rate bounced around his xK% and his six-year average xK% and K% are almost identical. So he probably doesn’t have some skill not captured here, unless he learned it overnight. Anyhow, his ascent into the elite has been pretty amazing. His SIERA has dropped every season beginning in 2009.

I ended with Trevor Bauer just to show how incredible his start has really been. Ignore the fact that he’s on an overperformer list and realize that my equation says his strikeout rate should still be above 30%! His swinging strike rate sits seventh in baseball and he’s also getting a high rate of foul strikes.