Around the beginning of the year, the Cardinals lost Adam Wainwright, and though they just welcomed him back to the active roster, there’s no time to build him up as a starter. Around the end of the year, the Cardinals lost Carlos Martinez, and while the hope is that there’s nothing seriously wrong with his shoulder, he won’t pitch again for a while. It speaks to the Cardinals’ organizational talents that Martinez developed into a quality option, and it speaks to their depth that his absence can be survived, but it puts a little more pressure on everyone else. Everyone includes Michael Wacha, but Wacha had himself a miserable September.

It was capped off Wednesday with a four-inning, six-run outing. Everyone’s allowed the occasional clunker, but it gets worrisome when a pattern develops, and in Wacha’s five September starts, he gave up 21 runs in 24 frames, with about as many walks as strikeouts. The obvious initial guess is fatigue. Wacha had a start skipped at the beginning of the month with his innings total in mind, and he’s cleared last year’s pitch count by about 1,200. And, absolutely, he might just be tired. Or it could be something else. There’s no reason to go with the initial guess and just stop there, when some research can be done.

Wacha has been a regular starter for the Cardinals since September 2013. He hasn’t often looked like he’s looked this past month, but in case you’re unconvinced, here’s a rolling-average plot, with five-game averages of Wacha’s strike rate.

One of the things about Wacha — when he’s right, he’s a strike-thrower. He throws about two-thirds of his pitches for strikes, which is comfortably better than average. Never before has he been in a serious extended strike slump. His rate the last five games is 60%, and until now he’d barely ever spent any time below 65%. Since becoming a regular starter, Wacha’s had six starts where he fell short of 60% strikes. Three of them have come in his last four outings. If this isn’t a real slump, it’s a hell of a coincidence. It sure looks like Wacha is fighting through a spell of sub-normal command.

You turn to the usual thoughts. How do you explain a pitcher slumping? I don’t think this is a case of bad luck. It’s not just about getting BABIP’d to death. Could be, it’s just randomness, noise sculpted to look like a signal. But, the reduction in strikes is suggestive. Is it fatigue? Is it an injury? Is it mechanics? The dirty and annoying little secret is it always comes down to mechanics. Fatigue can be evident in mechanics. Injuries can be evident in mechanics. And sometimes mechanics just go awry on their own. Identifying causes is the hard part, but at least we’re able to investigate this better than before.

That’s in large part thanks to Brooks Baseball. Analyzing pitchers is complicated, but they make it as easy as it can be. You can examine pitch locations over time. Same with pitch velocities. Same with release points. You can bounce around different options until you find something, if there’s something to be found. You can do it all in a couple of minutes. With Wacha, there’s no meaningful drop-off in velocity of late. There’s no increase in mistakes at the belt. There’s no big change in the vertical release point. There’s an increased tendency to throw pitches to Wacha’s glove-side. And, potentially related to that, we observe the following with Wacha’s horizontal release point:

That shows Wacha’s whole big-league career. On the y-axis, 0 refers to the middle of the rubber. Negative numbers are toward third base. There seems to be a trend in 2015, really taking off this past month. Wacha’s been releasing the ball closer and closer to the middle of the rubber. Every so often, you see a pitcher change the side of the rubber he stands on, but that isn’t what Wacha’s done. This is a subtle mechanical thing, and visuals could certainly help.

I’m going to show you a pair of a pair of pitches. Wacha started in Pittsburgh on May 8, and he started in Pittsburgh on Wednesday. Not only is Wednesday the most recent game — Pittsburgh also has a kick-ass camera angle. So that makes this easier. The pitches, specifically, weren’t chosen for any particular reason, except that I wanted them all to be against hitters on the same side. You should be able to spot changes even before I write more words.

The red lines aren’t indicating Wacha’s spine or anything — they’re tracing, approximately, the visible angle of his right side. Wednesday, the angle was tilted more to the left. You just get the sense of his no longer having just the right drive-line. Ray Searage works with his pitchers a lot on channeling everything in a line from the mound to the plate. With Wacha, look at some other indicators. His back foot, for instance. Wednesday, it came up at an angle, instead of in line with the catcher. The head position, too, is notable, and easy to compare. In the images from May 8, Wacha’s head is seen in front of the inner chalk of the lefty batter’s box. In the images from Wednesday, his head is seen within the box itself. Follow on up and you see a different release point. It’s shifted more to the left.

Wacha still wants to throw to the same place — straight ahead — but it’s as if his body wants him to throw to an imaginary zone somewhere behind a left-handed hitter. He just doesn’t seem as direct. And maybe this all comes down to his front foot. In the images from May 8, Wacha plants more or less in front of the center of the rubber. Wednesday, Wacha planted more to the left side, and maybe that pulled him in that direction. Maybe he’s just over-striding, and that’s causing him to go slightly off-line. Not so far off-line that he’s unrecognizable, but far enough that he struggles.

Look at it like that, and it seems so simple. Those are little changes to Wacha’s mechanics. His numbers have gotten much much worse. As an explanation, it makes sense to me, but I don’t want to pretend like I’m the authority here. For all I know, this is a deliberate adjustment Wacha’s making. While he’s thrown 60% strikes in September, he threw 65% strikes in August, and the trend had already begun. It’s gotten more extreme in September, sure. I just don’t want to pretend like this is so clean. It’s always complicated. We don’t know much about what’s happening behind the scenes. And if I can spot something on my laptop, the Cardinals must be able to see the same stuff.

For lack of better alternatives, I’ll buy what’s presented above. My best guess is that Wacha is off because his mechanics are off, and his mechanics are off in a way that sees him deviating from a straight line to home. Now, is that because he’s wearing down, or is that just because his mechanics are off, which happens to some guys for almost no reason? That part, I know I can’t answer. That part, we’ll possibly learn about based on how Wacha is used moving forward. If it’s just a mechanical thing, it could be worked on in side sessions, but Wacha won’t have another regular-season start to get straightened out. So, there’s a good deal of risk. Could be, I’m way off base. Could be, Wacha is actually just fine. He sure doesn’t look like it, though. And the games are about to get super important.