Jake Arrieta’s Been Off for Several Weeks

Ah, this part. I always enjoy this part. Not because I enjoy when superstars struggle, but because I enjoy seeing the standards to which we hold those same superstars. The standards are revealed when people start to worry. Over his last…I don’t know, eight starts, Jake Arrieta has a 3.77 ERA. He’s allowed a slugging percentage of .331. This is Jake Arrieta in a rut. I mean, this really is Jake Arrieta in a rut — people aren’t making up the rut — but you can see how silly reality is. That all-time amazing version of Arrieta became the version we allowed ourselves to take for granted.

But, heck, where’d he go? Arrieta himself would admit he hasn’t been firing on all cylinders. He’d like to pitch better than he has. The Cubs would like him to pitch better than he has. While Arrieta hasn’t been bad, lately he’s fallen short of expectations. And if you examine the record now, you see signs that Arrieta has been off to some degree for several weeks. This isn’t all that recent of a thing.

To repeat, it’s not as if Arrieta has been broken. For the most part, he’s continued to get outs. His strikeouts aren’t yet suffering, and he’s not getting hit all around the ballpark. By Statcast’s exit-velocity statistic, early Arrieta was solid. He’s stayed pretty solid. Jake Arrieta isn’t getting knocked around. The issue is that his command has suffered. Arrieta hasn’t been locating like he likes, and though opponents haven’t taken advantage by racking up extra-base hits, walks are walks, and baserunners are baserunners.

Some handy plots can give us a sense of the timeline. The walks? Here are Arrieta’s walks, in rolling seven-game samples:

This year doesn’t look much like last year. It doesn’t look much like the year before. Arrieta has spent a lot of this year north of that average baseline, whereas last year he was almost always under it. All right, let’s follow this. Arrieta says he simply needs to stop falling behind. He’s not wrong. Here’s another rolling-average plot, this time showing first-pitch strike rates:

A few things are of note here. One, obviously, of late Arrieta has been throwing too many first-pitch balls. But it might be some consolation to see that he did this for a stretch later last season, and also in the season before. This isn’t something he wants to be having happen, but it doesn’t necessarily have to be toxic. Arrieta, in the past, has been able to rally. This next plot is, I think, the most meaningful one. It’s also simple: A rolling-average plot of overall strike rate.

This is the one I don’t like, for Arrieta. The walk-rate plot wasn’t great, but that shows walks over all plate appearances. This shows strikes over all pitches, and that comes with a way bigger denominator. This is where I really see the recent problems. Over his last seven games, Arrieta has thrown just 60% strikes. He spent most of last year close to 65%. Arrieta hasn’t been this low over a seven-game stretch since settling in with the Cubs. By no means do I intend to suggest that Arrieta has somehow regressed to what he was as an Oriole, but his pinpoint location has been failing him. He hasn’t thrown enough strikes early, and he hasn’t thrown enough strikes to battle back. Left-handed hitters, in particular, have been content to wait Arrieta out. Last year, overall, Arrieta threw strikes with 65% of his pitches. He hasn’t hit that mark in even a single game since May 25. That’s eight starts ago.

As isolating the issue goes, it’s obviously very complicated. You always wonder about some injury, but for whatever it’s worth, Joe Maddon isn’t concerned about that.

“If he was injured, I’d be more concerned,” Maddon said. “He’s not injured. That’s the reason I feel he’ll be fine.”

We probably just have to assume Maddon is correct. He might not be, and sometimes injuries are hidden and relatively pain-free, but we don’t have enough to state conclusively that something is badly wrong. Now, a lack of command is worrying. It’s also worrying that Arrieta is coming off his lowest average velocity in a while. But, some kind of mechanical kink is more probable. Let’s just say it’s mechanics. Borrowing from Brooks Baseball, you can see that hitters have been less willing to go after Arrieta’s slider and curveball:

Maybe you think of it as a cutter, and not as a slider. I don’t care! It doesn’t matter. This plot shows swing rates against those two pitches, combined, and the swing rate has dropped. Don’t get too thrown off by that point for July 2016, since that’s just one game, but it doesn’t mean nothing. Arrieta has been less able to throw strikes with his breaking balls. Hitters have been less willing to swing at them. This has all put more pressure on Arrieta’s two-seamer, and no pitcher wants his repertoire to be narrowed.

And now here we see something interesting. A few years ago, Arrieta threw 48% fastballs. Last year, he threw 51% fastballs. Earlier this year, he was at 61%. More recently this year, he’s been nearer to 70%. So even to start with this season, Arrieta was throwing more fastballs and fewer sliders and curves. This pattern has only been amplified during recent struggles. This is a big deal. Arrieta’s curve has been important for him. And the previous two years, Arrieta’s slider was one of the very most valuable pitches in the game. It was arguably the whole difference-maker, and you don’t see pitchers go away from their best pitches like this for no reason. The best version of Arrieta has a dominant slider. Of late he’s been less willing to throw it.

We have a great pitcher with great breaking balls, throwing fewer breaking balls. Hitters are also swinging at those breaking balls less. There are a few ways one could try to interpret this. Could be Arrieta has lost some confidence in his secondary pitches. Maybe he just doesn’t have the right feel, and that’s also why he’s more often missing the targets. Or, could be this is out of an interest in self-preservation. Arrieta knows he just threw a ton of innings. Maybe he figures this way he’s less likely to get hurt. A season like Arrieta’s 2015 takes a toll, and it’s not like the various Mets starters have all been healthy versions of themselves. Pitching is dangerous. You might’ve heard.

Whatever’s going on, Arrieta isn’t broken, probably, but he isn’t quite Jake Arrieta. Strikes just haven’t been there in more than a month, and where a year ago Arrieta’s slider was worth +24 runs, this year he’s sitting just below +2. The Cubs say Arrieta isn’t hurt, and Arrieta himself says the fix is to more frequently get ahead. Of course the fix is to more frequently get ahead. The question concerns what he’ll have to do to do that. It’s been a while since Arrieta was on top. It’s been a longer while since he wasn’t.