On Sunday, and for the second time this season, Mookie Betts launched three home runs in a game. He now has 26 home runs on the season; for comparison, Giancarlo Stanton has 25, Chris Davis has 24, and Mike Trout has 23. Mookie Betts has a higher isolated slugging percentage this season than Miguel Cabrera, Ryan Braun, or Carlos Gonzalez. This is not what anyone expected.
I’ve long been one of Betts biggest supporters, but it’d be dishonest to pretend that we saw this coming. Even back in 2014, when I wrote the “Don’t Trade Mookie Betts” post extolling his value, I included the following paragraph.
Due primarily to his size (5-9) and the potential limits that puts on his power, Betts has not generally been viewed as a franchise cornerstone type of prospect the way Xander Bogaerts was as he ascended the ranks. And while it might seem unfair to make generalities about Betts’ future based on his height, there is merit to the idea that he probably won’t become a big-time power hitter in the big leagues.
In that piece, I noted that Betts’ combination of a low swing rate and a high contact rate put him in the company of mostly low-power slap hitters, but noted that it looked like he had enough doubles-power to become a Matt Carpenter or Ben Zobrist type of hitter, and those guys were worth holding onto. I liked Betts a lot, but I liked him because of the overall game, not because I thought he was going to turn into a slugger.
Even the following spring, when Betts went bananas in the Grapefruit League, his teammates sought to praise him by comparing him to Andrew McCutchen. And those comparisons were met with pushback, even by myself, as I continued to not see that kind of power development as Betts’ likely path to success. But now, a year and a half later, the McCutchen comparison looks wrong not because Betts didn’t develop McCutchen-level power, but because he’s already surpassed McCutchen-level power, and has become a very different player than he looked like coming up through the minors.
In the minors and even in his first half-season in the big leagues, Betts was a guy who took a lot of pitches, drew a bunch of walks, and succeeded by emphasizing the value of getting on base. But Major League pitchers decided to challenge Betts, giving him a high rate of strikes in order to force him to hit his way on board. It took a little bit of time, but Betts made the adjustment, and started looking for strikes to jump on instead of working counts.
The result is that Betts is putting up a season entirely unlike anything he’s done before. His current 6% walk rate is the lowest he’s posted in any professional season, but he’s offset the lack of walks with the upticks in power, and so instead of becoming a McCutchen-like all-around hitter, he’s succeeding with a line that looks like something straight out of an aggressive-slugger’s career.
For historical context, let’s go back 20 years, and look at under-25 hitters who have put up similar offensive seasons. To filter for similar lines, we’re going to look for players with a walk rate between 4%-8%, a strikeout rate between 10%-15%, and an ISO between .200 and .300. These are the guys who have had similar offense seasons at a young age.
Vladimir Guerrero! There’s a guy I wouldn’t have ever expected to compare Betts to, as from a raw skills standpoint, they really couldn’t be much more different. But his age-23 season is actually quite similar to Betts’ age-23 season, even though the physique and approach to hitting are polar opposites. Hanley Ramirez makes a bit more sense, as he also came up as an athletic middle infielder who turned out to hit quite well, but still featured an all-around game early in his career. Nomar Garciaparra continues the Boston connection, but like Guerrero and Ramirez, he was known as a guy who swung at everything and made up for his approach with remarkable plate coverage.
The funny thing is that Betts is getting results like those guys, but he hasn’t transformed into a free-swinger. He’s offered at 41% of the pitches he’s been thrown this year, well below the league’s 47% average, and while he’s expanded the zone a little bit compared to where he was in his rookie season, his 26% O-Swing is still a good bit under the 30% average of the rest of the league. Betts is, by any measure you want to use except for walk rate, still a selective hitter at the plate.
But as I showed back in June, Betts is still getting pitched like a slap hitter. I’ll borrow an image from that post a couple of months ago about the need for the league to adjust to Betts’ new-found power.
That graphic showed that Betts, despite a .225 ISO over the last calendar year, had the fifth-highest Zone% of any qualified hitter in baseball. If we updated the graphic for last calendar year from now, Betts would have the fourth-highest Zone% in baseball despite a .240 ISO over the last 365 days. This remains incomprehensible; Betts is slugging like a cleanup hitter but seeing strikes like he’s Ben Revere. The league continues to not adjust to Betts’ development, and he continues to punish them for it.
Eventually, we have to expect rational behavior to kick in, and for pitchers to stop throwing Betts middle-middle and middle-in fastballs that he can turn on. At some point, the scouting report on him has to change, and when they start pitching him more carefully, the walks should come back, and the power will probably come back down a bit. After some more adjustments, Betts may indeed settle in as an Andrew McCutchen type of hitter.
But right now, with how he’s being pitched? He’s more like Guerrero, Ramirez, or Garciaparra. Or peak-level Robinson Cano. His 2016 season looks like something that would fit in perfectly with Adrian Beltre’s career. A low-walk, high-power superstar? This is not the Mookie Betts any of us were expecting.
Dave is the Managing Editor of FanGraphs.