Pitchers Have Taken Notice of Mookie Betts

It’s been pretty much impossible to ignore what Mookie Betts has been up to. I know that FanGraphs has been rather pro-Betts from the beginning, but even we didn’t think he was likely to hit for this much power. So, he’s exceeding everyone’s expectations, on the way to becoming a legitimate candidate for the league MVP. Dave has written about Betts plenty. He just wrote about him the other day, in fact. And there’s one thing Dave has pointed to a few times: Pitchers should probably change the way they’re pitching. They look at Betts and see a little guy, so they’ve peppered the zone. Results would suggest they should attack with greater caution.

Even now, Betts still sees a lot of strikes. That much, there’s no denying, and any downward trend has been gradual. Maybe that’s going to prove to be a lagging indicator — maybe we shouldn’t expect the zone rate to plummet until 2017. But an adjustment has taken place. It’s been quiet, and it hasn’t even worked out to this point, but pitchers have caught on to the fact that Betts represents a hell of a threat in the box.

I’m going to do this in reverse of what’s typically recommended. Instead of starting strong, I’ll start weak! Let’s look at where pitches against Betts have been located. I grabbed the PITCHf/x data for his entire big-league career, and below I’ve plotted a rolling average of horizontal locations. The units are in feet, and 0 represents the middle of the plate, with a positive number meaning locations away.

The line clearly bounces around. From the beginning, pitchers started working Betts more and more away. Then a strong adjustment was made, with pitchers coming in more, but then that gradually went away again. Lately the pattern has repeated. The turning point is around the All-Star break. Leading into that, pitchers had become more confident approaching the inner half. Since then they’ve run away scared. Pitchers of late have tried to stay away.

That being established, now let’s look at vertical locations.

Generally, over time, pitchers have worked lower and lower. There have been hiccups, but lately, Betts has been pitched about as low as ever. Now we can put these together, calculating average distance from the center of the strike zone. That plot:

This gets to what Dave has argued for — pitchers have become less aggressive, if only lately. This plot has reached a new high, in terms of average distance from the zone middle. I can’t imagine it’s an accident; pitchers don’t want to groove the ball anymore. They recognize that Betts can do more than slap singles. He’s becoming a power threat, and now we can finally look at the strongest evidence. There are a few ways for pitchers to be aggressive. They can throw a lot of strikes, and they can throw a lot of fastballs. They’re throwing Betts fewer fastballs.

That plot — that plot is striking. You see a pretty consistent fastball rate, and then within the past month or two, there’s been a slide. Betts has seen less than 50% fastballs, where he spent much of his career closer to 60%. I’m going to guess this helps explain the trends observed earlier. If pitchers are coming after Betts with more secondary stuff, well, secondary stuff isn’t supposed to be around the middle of the zone. Caution is being exercised. Maybe not enough caution, yet, but Betts’ progress hasn’t gone unnoticed.

In the first half, 10 Red Sox hitters batted at least 100 times. Betts ranked fourth in fastball rate. In the second half, 10 Red Sox hitters have batted at least 50 times. Betts ranks ninth in fastball rate. To provide a league-wide context, there are 124 hitters who have been qualified in both halves. Betts’ fastball-rate drop of 9.3 percentage points is the second-biggest, behind only Justin Turner at 10. I’m not saying something flipped specifically at the break, but something did change right around there, so the splits work as a proxy.

The drop is significant, and it reflects Betts’ ability to murder the heaters he sees. People have always talked about his quick hands. They’ve always said he’s fast enough to cover heat that tries to get him jammed. This season, Betts has put everything together. In 2015, among qualified hitters, Betts ranked 72nd in runs above average against fastballs. Currently, he ranks 12th, one place below Mike Trout. When Betts has seen fastballs, he’s attacked fastballs, and so now pitchers are trying to do something different. You can’t blame them, although Betts is probably good enough to succeed no matter what.

This could end up being his shift. Betts in the past has discussed a need to be more aggressive, because big-league pitchers are around the plate. Betts started swinging more than he used to, and now he’s folded in good power. What will probably happen is that, as a result, he’ll chase opponents out of the zone, throwing more secondary stuff like they’ve already done. That’s how pitchers respond to power. If Betts doesn’t handle that well, he could get caught in between. More likely, he does handle it well, and then the walks will show up. And maybe some reduced contact, I don’t know, but if Betts draws more walks, he will have earned them through punishing strikes. Andrew McCutchen forced pitchers out of the zone when his power arrived. Pitchers aren’t aggressive forever when they get hit around, and we’ve known Betts has a good eye from his time in the minors.

A transition has been taking place. Mookie Betts has transitioned into being an all-around threat. And pitchers, in turn, are transitioning into being less aggressive with him. It makes all the sense in the world, when you think about it. We’ve all been surprised by Betts’ blossoming pop. Pitchers are the ones who have to try to do something about it.