It’s Time for the League to Adjust to Mookie Betts

Last night, in Baltimore, Mookie Betts did this.

Those three home runs pushed his season total to 12, putting him in a tie with guys like Mike Trout, Miguel Cabrera, Giancarlo Stanton, and George Springer, among others, and ahead of a group that includes Jose Bautista, J.D. Martinez, and Miguel Sano. Through the first two months of the season, Betts is hitting for the kind of power you expect from a slugging cleanup hitter, not a diminutive leadoff guy. And while Betts hasn’t had any three-homer nights before, this power surge isn’t that new.

Betts was excellent during his debut in 2014, but productive in the expected way; he drew some walks, didn’t strike out, and racked up a bunch of singles and doubles. The same was mostly true last April and May, though a BABIP drop led to his overall production sinking, and questions started to emerge about whether Betts was worth all the hype. Then, last June, Mookie went off, hitting .330/.375/.567, as 14 of his 32 hits that month went for extra bases. And he hasn’t stopped hitting for power since.

Over the past year, Mookie has now hit 25 home runs in 675 plate appearances, and when you toss in the 53 doubles and triples that he’s also hit — he’s tied with Jose Altuve for most non-HR extra base hits over the last year — you can see why he’s putting up a top-25 ISO over that stretch.

And yet, opposing pitchers keep challenging the Red Sox right fielder, in a way that they’re not challenging any other hitter in baseball who is hitting the way Mookie Betts has been hitting.

Here on FanGraphs, we track Zone%, which measures how often pitchers throw pitches in the strike zone to a particular hitter. The league average is around 48%, and then there’s about a five percentage point swing in either direction, so the range of Zone% in the big leagues is about 43% to 53%. Here’s how all the qualified hitters over the last year stack up in Zone%, with their ISOs also plotted as a reference.

As you’d expect, the higher Zone% marks are all to the left side of the graph, which corresponds to having a very low ISO. The hitter that is challenged most often by pitchers (53%) is Ben Revere, because he has an .073 ISO, and can’t really hurt you even if he hits it as hard as he can. Also at 53% is Billy Burns, the A’s speedy non-slugger, who is essentially a Revere clone with his .087 ISO. As you move right on the graph (and thus going up in ISO), you find much lower Zone% marks, as pitchers don’t challenge hitters with power.

Except, you know, that one solitary dot in the upper right corner. That’s Mookie Betts, in the square all by himself, sitting at a 52% Zone% and a .221 ISO. Despite that top-25 ISO, he’s seen the fifth-highest rate of strikes of any hitter in baseball over the last year, and pitchers are challenging him at the same rate they’re challenging Derek Norris, Martin Prado, and Chris Owings.

At some point, you’d think the league would notice that pounding strikes to a guy who can crush them isn’t working, but no, there’s no real signs that the league is adjusting their approach to Betts in a significant way. In the second half of last year, after his monster June showed everyone he could hit for some power, pitchers threw strikes to Betts on 51% of the pitches he saw, and he made them pay repeatedly. This year, with plenty of time to adjust the scouting report and come up with a new plan to account for Betts’ four-month power spike, pitchers have thrown strikes to Mookie 52% of the time.

Those numbers are down slightly from his 2014 debut, when pitchers challenged him 53% of the time, but overall, he’s still being pitched to like he’s a 5’10 slap-hitter. But we’re now a year into the Mookie Betts, Power Hitter era, and it seems like it’s time for pitchers to try something new. After all, it’s not exactly a secret where Betts’ power comes from.

Mookie likes the ball middle-in, and if you give him something on the inner-half of the plate, there’s a good chance he’s going to turn on it. As August Fagerstrom wrote here back in April, Mookie is a very similar hitter to Dustin Pedroia, another diminutive Red Sox hitter who has made a career out of pulling the middle-in pitch to generate more power than you’d expect from a guy his size. And interestingly, pitchers never really stopped challenging Pedroia either; he has a career 53% Zone%, and has never been under 51% in any single season.

But with Pedroia, it’s at least slightly more understandable. Pedroia’s never hit more than 21 home runs in a season, and he reached that mark in a year where he came to the plate 735 times and only had 40 other extra base hits. His highest full-season ISO is .167, a mark Betts already beat last year, in his age-22 season, his first full year in the big leagues. While August notes many similarities between the two players, Betts appears to have more power than the second baseman who forced his position change, and is more capable of punishing mistakes over the heart of the plate.

As Alex Speier noted in a Boston Globe piece on the subject earlier in the week, people have been looking at Mookie Betts and assuming he’s too small to hit for significant power for years.

“As I was younger, kids would move in. When you see a small hitter, kids would move in. Coaches would move them in. My dad would really just say, ‘Hit it over their head.’ For some reason, I was always able to do it, even being a little smaller,” said Betts.

Coaches aren’t still bringing the outfield in when Mookie comes to the plate, but the big league version of that idea is to still challenge little guys in the zone as often as possible. With Ben Revere and Billy Burns, it’s a good idea. But it’s time for the league to realize Mookie Betts isn’t Ben Revere or Billy Burns. He might not keep running a .220 ISO, but this is a guy who punishes mistakes, and it’s probably time for pitchers to try something else besides challenging the little guy at the top of the Red Sox lineup.