Yesterday’s big news was that the Nationals agreed to a long-term extension with Stephen Strasburg. So that’s exciting for him, and for them, but you always have to think about the side-effects of these things. Several people pointed out that, without Strasburg, the upcoming pitching market sucks. And several people also pointed out that, with Strasburg locked up, this puts Billy Beane in a better position with regard to Sonny Gray. There’s just the one problem right now: Sonny Gray hasn’t been very good.

He’s far from the only ace who’s had his struggles. If you look at all the qualified starters and sort by ERA, you see David Price at an unbelievable 6.75. There’s Adam Wainwright, with an uncharacteristic 6.30. Gray is hanging out at an even 6.00, after getting tattooed by the Red Sox. Every slump is accompanied by a search for explanations. Seems to me the explanation for Gray is that he’s been pitching without his best weapon.

Over and over, Gray has insisted he feels great. It’s what’s made this all the more perplexing — we can’t chalk anything up to illness or discomfort. Not that Gray couldn’t be lying, I guess, or not that there couldn’t be something subtle underneath, but he feels good, and his velocities are good. His arm slot is normal. The worry is always injury. I get it, but injury isn’t always the root cause for something. More common, I believe, is a mechanical slump. That’s my guess on this one.

And whatever it is, it’s costing Gray his breaking ball. The breaking ball is what made Gray an elite-level prospect. The breaking ball is what allowed Gray to become staff ace at a young age. He’s still using it, because he still needs to use it, but Gray has been missing his usual feel, and that’s something he needs to straighten out.

Gray told Eno a while ago that he sort of has one breaking ball and two breaking balls. He has one grip, but he’s had a tighter breaking ball and a slower breaking ball. One that looks more like a slider, and one that looks more like a curveball. Consider now the following plots, showing Gray’s breaking-ball velocities and spin axes over the past three years. Something should jump out to you.

It used to be easy to identify two groups. There was the harder, slider-y one, and the slower, curvier one. Last year, the groups came together a little, but this year the situation is different. This year the slider-y cluster has mostly gone away. When Gray has gone to his breaking ball, he’s mostly thrown the curveball version, and since the slider version has been good for him before, that doesn’t seem like it should be something planned. It seems like Gray hasn’t been comfortable mixing up his arm actions.

And the breaking ball that Gray has thrown hasn’t behaved like he’d like. These are some heat maps from Baseball Savant. Gray’s struggles have been ugliest against right-handed hitters, and these plots show something dramatic. Here are Gray’s breaking-ball locations against righties, since 2014:

This year has been a mess. It’s one thing to throw breaking balls just off the plate, or just barely out of the zone, but Gray’s location has been way off. It seems like he’s been holding the ball too long, resulting in a bunch of pitches so low they can be mentally eliminated. Now, breaking balls below the zone are better than breaking balls left hanging, but if as a hitter you see that Gray isn’t controlling his breaking ball well, you can hunt for that fastball. And, mostly, the fastball has gotten hit. Last year, by our run values, Gray’s fastball was worth 16 runs better than the average. This year he’s already almost at -5.

And the breaking ball is worse, of course; it’s gone from +14 runs to zilch. The breaking ball hasn’t been directly punished, but because Gray hasn’t thrown it for strikes, it’s allowed the rest of the repertoire to get punished. This is a great example of the cascading effect of one pitch going from a zone rate of 41% to a zone rate of 28%. Everything works together, and if you take away a key component, the whole structure can collapse.

In Gray’s defense, he’s probably been a little better than a 6-flat ERA. The A’s haven’t given him too much defensive support. And against the Red Sox on Monday, Gray got his breaking ball up a little more, but his control was still off, and lifting his breaking ball caused him to also lift his fastball. It was an attempt, but it wasn’t a solution. Gray’s still searching for his solution, which is probably a minor tweak or two away.

I don’t know what those tweaks are. And I can’t promise that this isn’t because of some physical malady. I just don’t want to assume injury without any other signs. When it’s not injury, the explanation is usually that the mechanics are off, somewhere, somehow. Gray’s mechanics have cost him the breaking ball that for the most part put him on the major-league map. Pitchers tend not to suddenly lose their best weapons for good, but when they go into hiding, there’s not much left for a pitcher to work with.