Tommy Kahnle’s crumbling cambio

When the Yankees ended the first half seven games above .500, their bullpen was arguably the league’s best — the unit’s 3.09 ERA tied for first. But a FIP more than half a run higher portended regression, and sure enough, their ERA has risen to 3.48 since the All-Star break, a mark that ranks seventh in that time. That’s still pretty good, and the ‘pen wasn’t that much worse during the recent nine-game losing streak — their ERA was only six points higher — but the opposition did hang three losses on them. One of those L’s went to Tommy Kahnle, who’s been responsible for a good chunk of that bullpen regression. Case in point, he shouldered another loss just yesterday.

But these two recent losses are merely a continuation of a trend in the wrong direction for Kahnle in the second half. In fact, his season-starting 15.1-inning scoreless streak ended his first day back from the All-Star break, July 15th. Since, he’s pitched to a 6.14 ERA in 14.2 innings, allowing five homers along the way. At first glance, it’s hard to see any changes that can explain this shift. His pitches have maintained their shapes, his fastball velocity has gone up a tick, and he’s turning to his best pitch, the changeup, even more often.

At the same time, the changeup is performing a lot worse on contact. On 32 balls in play since the scoreless streak ended, opposing hitters have managed a .445 wOBA — well above average, and that’s not even counting the two homers he gave up on the changeups in yesterday’s contest. Meanwhile, during the streak, hitters put up just a .208 wOBA on 29 balls in play. These are small samples to be sure, and the closer xwOBAs — .344 vs. .280 — mirror this fact, but there’s a divergence even there.

What’s driving this? I can think of two reasons. First, while it’s generally good to throw your best pitch more often, perhaps Kahnle’s reached the point of diminishing returns with his change. Of all pitches, the changeup in particular plays off the fastball, and it’s reasonable to think that Kahnle needs to start throwing more heaters again.

What might be the breaking point for Kanhle’s changeup? He ratcheted its usage up to a career-high 76.4 percent last year and found a good deal of success in 12.2 innings with the Dodgers. During his scoreless stretch this year, he turned to the cambio a near-identical 76.3 percent. But Kahnle’s last appearance in that excellent span also happened to be the last time he threw the changeup less than 70 percent in an outing. Overall, he’s thrown it 6.6 percent more in the second half.

The other issue is that he’s switched up the locations on the pitch a bit. Below left, from the catcher’s point of view, are changeups Kahnle threw during the streak, and below right are those he’s thrown since. He’s throwing more changeups glove-side in the zone; given that changeups run arm-side, that means that these pitches will start as strikes and stay that way, taking the difficult part out of a hitter’s swing decision. Meanwhile, he’s throwing fewer changeups off the plate arm-side; those would start on the plate and then run in on a righty’s hands or off the plate outside to a lefty. He’s throwing more changeups down too, which is good given the natural sink on the pitch, but these would work better if they were paired with high fastballs more often.

Kahnle’s stuff is still of the same quality, and a pitch mix change won’t run the risk of forcing any mechanical changes. And as long as those location changes have been unintentional, they’ll be easy enough to fix. The Yankees have him under contract for next year; the opportunity is there for him to finish this season strong and carry that momentum into his walk year in the Bronx.