Looking At Strikeout Rate Changes After 70 Batters Faced

We know very little this early into the season. Your Roto position matters little, your sleepers struggling doesn’t mean a great deal (unless it can impact playing time, and closers, well, we know about as much now as we did in the preseason: zilch.

However, the “small sample size” caveats will, eventually, begin to fade. And in fact, there may actually be some information we can glean from the early going, at least as it pertains to pitcher strikeout rates.

Strikeout rates are among the first statistics to stabilize. “70” is not a magic number, but after about 70 batters faced, a majority of the future variance (R2=0.5) in strikeout rate can be explained by strikeout rate to date. That is, after 70 batters faced, pitcher strikeout rate has begun to “stabilize.”

What that means is that for the 65 pitchers who have faced 70 batters already this season and also faced 70 last year (sorry, Felipe Paulino), changes in strikeout rate may be indicative of unerlying changes. I pulled that sweet, sweet data, and here are the names making waves, good or bad.

Strikeout Percentage Gainers

Oh, Stephen Strasburg is getting even better, that’s not terrifying at all! The velocity dip might be of some concern for Strasburg – though velocity is generally lower in April and declines with age – but he’s missing more bats. It seems the increased usage of his changeup – up from 16.2 percent to 28 percent and with a 50 percent whiff-per-swing rate – is disagreeable for hitters. It’s only a 6.5MPH difference, but it seems to be fooling batters.

Meanwhile, Kyle Lohse is bringing additional heat, leading to his unexpected outing over the weekend. He’s just 48 percent owned in Yahoo leagues, and if the early-season changes in strikeout ability are at all indicated that he could be, say, an 18 percent strikeout guy, he’s worth a look.

Nathan Eovaldi and Jarred Cosart are perhaps the most interesting names on the list as they both entered the season to some degree of optimism, especially for Eovaldi, thought ZIPS didn’t like either for seven strikeouts per nine. Eovaldi isn’t throwing any faster, but he’s traded four-seamers for more two-seamers and sliders, per PITCHf/x. He’s getting whiffs on nearly 30 percent of those sliders, helping make up for the paltry 11 percent whiff rate on the fastball (Brooks Baseball doesn’t differentiate his two- and four-seam offerings). Cosart, meanwhile, appears to have traded in the fastball for far more cutters, which he’s thrown 72 percent of the time. That 94.1MPH heat certainly plays up if the ball is biting rather than flying straight, and the result has been not just an uptick in whiffs (16.1 percent from 13.6) but also groundballs (66.7 percent from 56.9).

And yeah, looks like I’ll be losing my “Andrew Cashner won’t be a top-70 starter” bold prediction (the others look solid, however).

Strikeout Percentage Losers

Sorry, but I refuse to say bad things about A.J. Burnett, ever. Love that guy. But the numbers aren’t friendly, to say the least. Sure, he had a down June last year (17.9 percent strikeout rate), too, and bounced back fine. He may want to move back to throwing more fastballs despite the velocity decline – while he hasn’t enduced a single whiff with it, the sinker is only getting whiffs 10 percent of the time (it was just 7.1 percent last year), and the fastball played pretty well last season (21.8 percent whiffs).

Tanner Scheppers wasn’t someone I was high on to begin with, and his stats are taking the move from bullpen to rotation poorly. A drop in strikeout rate is expected with such a move, and the groundball rate remains more than fine, but there’s going to be very little fantasy upside here if he can’t find a way to miss some bats with the heavy sinker he employs.

I’m not quite as sure what’s up with Julio Teheran, who hasn’t lost more velocity than the usual April half-mile dip but can’t seem to miss bats early on. It’s not the slider that’s been the issue, as he’s still getting whiffs on 41.4 percent of those and throwing a fair number of them, but the whiff rate is down on his other offerings, including the heater. Not only is Teheran missing slightly fewer bats, but batters are fouling off far fewer balls, down from 28.8 percent to 19.3 percent, per Baseball Reference. Trading fouls were whiffs or called strikes is great, but Teheran is trading them for balls in play right now.

A lot of the other names on here are very familiar, which shouldn’t be all that surprising – pitchers strikeout fewer batters as they age, and starters see a pretty big drop-off as they reach their late 20s. Ubaldo Jimenez? 30. Justin Verlander? 31. Ricky Nolasco? 31. Scott Feldman? 32. Jeff Samardzija? 29. Cliff Lee? Ageless. You likely priced in a strikeout decline for many of these names, so it’s not necessarily worth panicking about in some cases. I’d be very weary of Jimenez moving forward though, if you want one recommendation from this group – his ‘rebound’ last season was largely based on competition, and there are a lot of scary signs in his early-2013 profile that are resurfacing now.