Back in 2015, there were 643 different pitchers who threw at least 100 pitches. Out of that entire player pool, Carter Capps generated the highest whiff rate, and he had the highest whiff rate by nearly five points. Capps was as close to unhittable as any pitcher has ever been, really, and so we were fascinated, the whole lot of us. You can say you’re growing tired of strikeouts, but extremes are extremes. Capps was something else entirely. It was as if he’d been sent down from some hidden higher level.

Here in 2017, there are 604 different pitchers who have thrown at least 100 pitches. Out of that entire player pool, Carter Capps has generated the lowest whiff rate. He has a lower whiff rate than Christian Bethancourt, who wouldn’t be described as a professional pitcher. In a mop-up role last night, Capps struck out Kolten Wong. It was his first strikeout since returning to the Padres more than two weeks ago.

A lot has happened.

Capps certainly deserves the benefit of the doubt. At least, he deserves some of the benefit, because his 2015 season ended with an elbow problem, and it ultimately required Tommy John. The surgery and the rehab ate up Capps’ 2016, and so he’s only recently back. His recovery wasn’t as smooth as it’s been for other players, and I imagine the time missed and the opened-up elbow have something to do with this:

Capps used to sit around 98 – 99 with his fastball. Now he’s around 93, and he’s so far topped out at 96. What’s going on with Carter Capps? A pitcher won’t be the same guy without five whole miles per hour. What happened to his miles per hour? Some of it, possibly or probably, has to do with arm strength. Capps might still be building up. The surgery is only a year and a half behind him. It can take a while. Yet that isn’t everything. That can’t be everything. Few pitchers ever lose this much zip after having Tommy John, and the other half of the story with Capps concerns the way that he throws. You remember.

I guess we’ll have to do this again:

Capps turned into a high-strikeout pitcher, but he got a lot more attention than, say, Tommy Kahnle has, after becoming a high-strikeout pitcher himself. And it’s because Capps was so weird, and so controversial. In 2015, the Marlins let Capps do what he wanted, and what he wanted to do was leap. Leap forward as he threw, chewing up precious inches between the rubber and the plate. No one had ever seen anything like it. The league wasn’t entirely sure how to respond, and it settled on allowing Capps to keep it up, provided he dragged his back foot. That was the understanding, as Capps pitched, and then as Capps was no longer able to.

Several months ago, baseball formalized what had been its unofficial position. With Capps beginning to throw in spring training, the league issued the following modification:

An addition to Rule 5.07 stipulates that a pitcher may not take a second step toward home plate with either foot or otherwise reset his pivot foot in his delivery of the pitch. If there is at least one runner on base, such an action will be called a balk under Rule 6.02(a). If the bases are unoccupied, then it will be considered an illegal pitch under Rule 6.02(b).

That didn’t really demand that Capps do anything new. It simply made official that Capps couldn’t come completely off the ground. And yet, in effect, Capps found himself in the spotlight. He knew that the league would be watching. The story in spring was that Capps was working on his mechanics. The story into the early summer was that Capps was working on his mechanics. We’re able to see Capps pitching now, and he’s not the same guy. I don’t just mean in terms of velocity or results; Capps is visibly different. He’s worked for months to try to control his pivot foot — the back foot — and for one clue, look at the following pitch:

That’s from the other day. Compare that video to the earlier one. Or, if you don’t want to do that, then just look at these screenshots.

The camera angles aren’t exactly the same, which is a drag, but look at Capps’ back foot, relative to the rubber. In the earlier screenshot, from 2015, the rubber is nearly out of the frame. Capps is separated by, what, a foot? A foot and a half? In the more recent screenshot, you don’t see very much mound between rubber and cleat. Again, a different angle would be preferable, but it seems as if Capps has shortened his jump. His delivery has become a little more conservative, and yet, according to Statcast, he’s still getting the same forward extension as before. That’s not all coming from his leap — some other component is making up ground, which would leave Capps particularly stretched out.

It’s helpful, also, to watch Capps throw from a normal angle, at normal speed. So, 2015 and 2017:

There are more changes visible here, or, failing that, symptoms of changes. Here are some selective side-by-side screenshots:

In the first set, you can see that 2017 Capps is opening up earlier with his upper body, while his lower body is more closed. Move down to the next set and you see it again — Capps’ front shoulder is more open, and yet, with his feet, he’s closing himself off. Back in 2015, Capps threw while well-aligned with home plate and the catcher. This year’s Capps has been trying to throw across his body, which is generally inefficient. At last, in the final set, you see Capps’ follow-through. In the earlier picture, Capps looks like an ordinary pitcher. The ball is gone, and Capps’ back leg has come up. In the recent picture, the back leg is barely off the ground. Capps no longer lifts his leg and drops it back down. Now it more kind of just sweeps forward, gently. No pitcher is ever concentrating on what that back leg is doing during follow-through. It just happens automatically, as the result of everything else. But the follow-through is a tell. Capps’ delivery right now is less efficient, and less explosive. Watch it closely and you could probably assume lower velocity, even without a radar gun.

The good news, I suppose, is that Capps probably still has 99 somewhere inside him. I doubt it’s so much an arm-strength thing as it is a mechanical thing, and so, in theory, Capps would just need to get straightened out. He would have the potential to be dominant again. He just needs to throw the same way.

But, *can* he throw the same way? This is where it gets tricky. Some rustiness can be excused for any pitcher coming back from so much time off, but, from at least the beginning of spring, Capps has had to worry about the behavior of his back foot. No other pitcher really needs to do that. Capps is the only guy who jumps, so Capps is the only guy who needs to make sure he maintains contact with the ground. The league is watching closely. Umpires and opponents are watching closely. One can imagine it’s enough to make Capps feel preoccupied. He’s so focused on that back foot that it seems like he’s shortened his leap. That shortened leap might well have cascaded into other complications. Now the timing is all off, so the stuff is all wrong, and the results are unremarkable. Capps isn’t dominant at all. He’s not missing any bats.

The league formalized a sort of Carter Capps rule. Already, he had a noteworthy motion, but Capps found himself in the spotlight, as he was finishing his rehab. What the league didn’t do was make Capps’ motion illegal, but now you wonder if they might as well have, with Capps having to strike so fine a balance. His delivery is baseball’s most complicated. He has to worry about something that no one else does. I’m not sure if we’ll ever again see that old Carter Capps. He might’ve effectively been litigated out of existence.