Perusing the Last 30 Days AL SP SwStk% Leaders

I despise the use of small sample sizes, but pitchers change so frequently that it’s not so silly after all to evaluate shifts in underlying skills over a relatively small number of starts. So as I do every once in a while, I peruse the SwStk% leaderboard over the last 30 days. Let’s discuss some of the interesting names on there, shall we?

So Sean Manaea returns from a shoulder strain and goes on to lead the American League, nay, all of baseball, in SwStk%. When looking at his individual pitch results, it’s easy to see why — his four-seamer has been well above average at generating swings and misses, while both his changeup and slider have been elite. The latter two have both induced whiffs at an above 20% clip. He did nearly the same thing last year in his debut, though with a less whiffy fastball. What’s weird is his fastball velocity is down, yet it’s been getting far more whiffs. It’s odd that all the whiffs haven’t led to an even higher strikeout rate – but that’s because he isn’t throwing enough strikes and both his called and foul strike rates sit well below the league average. I care most about his whiff inducing skillz, so he is someone to be excited about.

I include Masahiro Tanaka here just as a reminder to how absurd his season has been so far. Despite all the whiffs, he has posted a 6.51 ERA over the last 30 days. For the season, his skills are nearly identical to last year, but his BABIP has surged above .300, while his HR/FB rate has nearly doubled. It’s all looking very CC Sabathian from a couple of years ago, except that Tanaka hasn’t lost ticks on his fastball. Come up with as many explanations to fit the results that you want — “his fastball is straight” or “his splitter isn’t splitting” — but he’s going to right the ship sooner or later, so he’s an excellent trade target.

Sonny Gray?! These are actually some of the best skills he has posted. The grounders have always been there, but now his slider is inducing whiffs like never before. With his ERA still over 4.00, it would be easy for his owners to feel like there is still a long way to go for Gray to return to his former vintage form. He actually already has, but the results have yet to catch up with such a fact.

I’m lumping Matt Shoemaker and Michael Pineda in together. High SwStk% aren’t exactly surprising for the pair, but what is surprising is the relatively low strikeout rates that have come along. Of my small data set of 42 names, the correlation between SwStk% and K% was a robust 0.78. So these guys seem to be suffering a bit of what Manaea has — an ability to generate whiffs, but that’s about it in the last month. Obviously, you’d like to see everything, but there’s less to worry about when the one strike type these pitchers excel at is of the swinging variety. The strikeouts will be there.

I had never heard of Jordan Montgomery and didn’t even consider him as a sleeper this preseason even as he was talked about as a candidate to win the Yankees’ fifth starter job. But heck, check out that history of SwStk% marks in the minors! Actually, you can’t see them on his regular page, but if you create a custom dashboard and add the SwStk% metric to it, then voilà, there it is. It’s not about the fastball velocity, and he has actually only thrown the pitch 43.5% of the time, but all three of his secondary pitches, the changeup, curve, and slider, have been fantastic. When you possess that many above average offerings, there’s a real downside cushion. Unfortunately, even with the solid strikeout skills, his SIERA still sits above 4.00, so it’s not like he’s someone to rush out and grab in shallow leagues.

Second time’s a charm so far for Jose Berrios. But, I’m skeptical. The issue here is that he’s primarily getting his whiffs from his fastball. His four-seamer is sporting an inflated 13.8% SwStk%, which is very high, while his curve and change are both well below average for the pitch, with the latter sitting in the high single digits. That’s not good. I can’t believe he’ll be able to sustain such a high whiff rate on the fastball, and he has nothing to fall back on when its effectiveness wanes. I’m selling high.

All these years, it always felt like Kyle Gibson could be on the verge of a breakout. Both his slider and changeup are fantastic at inducing whiffs, so he just needed to figure out how to improve that fastball from terrible to merely mediocre. These last 30 days has represented a nice jump in SwStk%, though the strikeout rate remains below the league average. Maybe he just needs to give up some grounders to get more whiffs, as clearly his current combination isn’t working.