What to make of Tommy Kahnle’s early struggles

Velocity is one of the more important things to keep an eye on early in the season. Unlike most statistics, which can take weeks and months to really become reliable, velocity tends to stabilize pretty quickly. Big leaps forward or steps backward in terms of velocity can be meaningful even in the opening days of the year.

I went through this earlier in the week in detailing the most significant velocity changers on the Yankees. Luis Severino and Aroldis Chapman profile as the two most important players to see changes in speed, but another name to watch is Tommy Kahnle.

Kahnle has been brutal so far in 2018. He was a boon in the bullpen after coming over from the White Sox midseason last year, but he has not been the same guy so far. In 7.1 innings, he’s struck out nine, but walked eight and yielded seven runs.

Not coincidentally, Kahnle has seen his velocity regress. Now, Kahnle has said that he feels the issue is mechanical, and can be fixed, and manager Aaron Boone has been optimistic that Kahnle’s velocity won’t remain down all year. It’s possible that this is just a blip on the radar.

But the actual numbers are startling. Through Baseball Savant, I pulled pitchers that have thrown at least 50 fastballs this year, and compared their 2018 velocities with their 2017 velocities. Here are the pitchers who saw their pitch speeds drop the most:

Kahnle is all the way up there. His velocity has fallen from pretty sensational in 2017 to fairly unspectacular for a reliever in 2018. At a near-three mph drop, it’s hard to believe Kahnle when he says this is all mechanical. It seems likely that some sort of physical change has to have occurred to spur such a massive change in velocity.

Even if the drop is to some extent attributable to mechanics, early season jitters, and cold April weather, the fact Kahnle has seen his velocity fall more than all but three other pitchers is cause for concern. Just how worried should the Yankees be?

Again, I used Baseball Savant to look at pitchers with similar velocity drops to what Kahnle has suffered. This time, I looked at pitchers that saw their velocity drop at least 2 mph from 2015 to 2016, and then looked at how their performance was affected:

On average, these pitchers had an 87 ERA- (park and league adjusted ERA, where 100 is average and lower is better) in 2015, and a 102 ERA- in 2016. There are some large changers here in this sample that can skew the numbers a bit, but still, the result is unsurprising. Pitchers that saw their velocity drop severely like Kahnle saw a corresponding drop in performance.

I repeated this exercise with pitchers from 2016 to 2017, and the results were as expected:

Again, pitchers that lose 2 or more mph on their fastballs get worse. Here, five of the six pitchers regressed in terms of run prevention, while Hunter Strickland was the only one who managed to get better.

None of this is entirely surprising, as velocity is vital to most pitchers, and a loss of it should typically correspond with a drop in quality. Now, with Kahnle facing a huge drop in velocity and the prospect of a fall in performance, is there any reason for optimism?

Perhaps at least a little. Going back to those who lost their speed in 2016, we have data in 2017 to see if they managed to bounce back. In fact, a few of those pitchers that lost their stuff in 2016 did see noticeable gains in 2017:

After suffering a huge drop in 2016, David Price, Madison Bumgarner, Jacob deGrom, and Carlos Carrasco all were able to make up some of what they lost. This is encouraging, as Kahnle, under team control through 2020, looks to be part of the Yankees’ plans for the foreseable future. There is precedent for a pitcher to lose as much velocity as Kahnle as and to regain a part of that loss in the future.

For now, though, Kahnle’s start the season looks like a major concern. The Yankees’ bullpen profiled as potentially historic prior to the year, but after a couple weeks, multiple members of that vaunted unit are struggling. Kahnle has exhibited scary warning signs early on. There is certainly hope that he can bounce back, this year or next, but at the moment, Kahnle doesn’t look as though he can be trusted the way he was down the stretch in 2017.