What happened to Jonathan Loaisiga against the Royals?

We’re 73 games into the season, and the bullpen has been the Yankees’ MVP so far. The rotation flashed its upside early before falling back to Earth, while the offense has played well short of expectations. If not for the shutdown work of their relievers — aside from a few bumps in the road of late — the Yankees wouldn’t be within sniffing distance of the AL East leaders. A key cog of that vital relief corp is Jonathan Loaisiga.

Loaisiga has been a revelation for the Yankees this season, taking a huge step in his development. Coming into Tuesday night’s appearance against the Royals, he owned a 1.63 ERA, a 64.4 percent groundball rate, and the third-most fWAR of any Yankees pitcher. His adoption of the sinker as well as reshaping his curveball and changeup — something I detailed in April — have paid huge dividends.

That is why Loaisiga’s blow up in the eighth inning of Tuesday night’s game came as such a shock. He recorded only two outs, giving up four runs on five hits before being pulled for Lucas Luetge. The deficit Loaisiga incurred proved too much for the Yankees to surmount, as they fell 6-5 in the series opener.

What was so bizarre about Loaisiga’s outing is that he deviated drastically from the formula that brought him so much success across his first 30 appearances. He completely abandoned the changeup on Tuesday, throwing exclusively the sinker and curveball. In doing so, he immediately became more predictable, with batters timing up the sinker with alarming regularity. Prior to that game, his sinker carried a .210 xwOBA, -5 degree launch angle, 76.1 percent groundball rate, 26.8 percent hard hit rate, and zero percent barrel rate. Those numbers worsened to .433, two degrees, 50 percent, 50 percent, and 16.8 percent respectively, during this outing.

The changeup is by no means Loaisiga’s best pitch — in fact it’s his third-best pitch by xwOBA — but what it does is make his other offerings that much more effective. Having the confidence to throw a third plus-pitch in any count keeps hitters honest against the real put-away pitches. The sinker gets on a hitter that much faster with the changeup in mind, while the curveball bends that much more relative to the opposite-breaking changeup.

The most interesting facet of Loaisiga’s nonuse of the changeup is that it coincided with the day umpires started checking for foreign substances. Is it possible that he didn’t feel comfortable throwing the changeup without the aid of a sticky substance? Unlikely, besides it would be irresponsible to speculate that A) Loaisiga had previously used a foreign substance and B) an inability to use it meant he couldn’t throw a changeup.

There are a multitude of explanations that don’t involve the crackdown on foreign substances. Maybe the Yankees gameplan for approaching the Royals hitters involved ditching the changeup — Gerrit Cole threw his lowest percentage of changeups all season. Or perhaps Loaisiga just didn’t have a good feel for the pitch while warming in the bullpen. Loaisiga’s decision to not use the pitch doesn’t have to involve a lack of access to spin-boosting grip enhancers. Besides, there is growing evidence that less spin is better when throwing the changeup.

Regression was always going to come for Joanthan Loaisiga. Chances were slim he would remain a top-ten pitcher in baseball all season. It’s just unfortunate that it all had to come crashing down at once and lead to a loss. The silver lining in all this is that the clunker (probably) wasn’t due to the foreign substance crackdown but rather a one-off shift in strategy, and that many signs point to a bounce-back in his next outing. There is no reason why Loaisiga can’t continue to be an invaluable contributor out of the Yankees bullpen.