How Mookie Betts Has Been Baseball’s Best Hitter

It’s not entirely clear anything was wrong with Mookie Betts in 2017. Yes, he finished with a wRC+ of just 108, after the previous season’s 137, but those numbers can occasionally mislead. Consider the Statcast-based expected wOBA, available to query at Baseball Savant. Betts, in 2015, had an expected wOBA of .335. In 2016, it was .336. In 2017, it was .341. I wouldn’t necessarily call that conclusive, but it’s evidence that Betts was just hurt by a little bit of bad luck. He remained a perfectly good hitter all the while.

In 2018, Betts has an expected wOBA of .602. He leads all qualified hitters in wRC+. Tuesday night, in a game started by Shohei Ohtani, Betts went deep three times. Betts won’t keep this up, because no one could keep this up, but it’s worth it to look under the hood. Betts’ scorching start has been a consequence of his hitting to his strengths.

There’s something about Betts that’s always been funny to me. From day one, Betts has been renowned for his discipline, and for his bat control. His bat-to-ball skills are among the best in the league, and few hitters seem to be so good in the area of pitch identification. Rarely can a pitcher make Betts look bad. But for as talented as he is, Betts has always been awful to the opposite field. Over his career, to the pull side, Betts has posted a 242 wRC+. Going the other way, that wRC+ sinks to a lowly 25. There’s a difference, therefore, of 217 points, which is the largest such difference in baseball since Betts was promoted. It clearly hasn’t prevented Betts from being successful, but if Betts is going to hit, he’s going to do his hitting in and around left field.

Let’s look at a couple of spray charts, also from Baseball Savant. On the left, last year’s Betts. On the right, this year’s Betts.

You can see a clear preference to hit to left field. It’s especially clear on the right. To make it easier to understand, we can draw a line up the middle of the field. Often, you’ll see the field split into thirds. I’m just using halves — there are pulled balls, and there are non-pulled balls. Here are Betts’ year-to-year rates of pulled batted balls, going back to 2015.

• 2015: 58%
• 2016: 54%
• 2017: 60%
• 2018: 84%

That rate for this season is the highest in the game. No one has pulled the ball as often as Betts has. Right away, that seems like a good thing, given Betts’ own background, but it would be fair to wonder if Betts is just rolling over on a bunch of balls. I mean, we already know he’s not, since we saw the spray chart, but sometimes guys get pull-heavy and they drill the ball into the ground. Typically, grounders are pulled, and fly balls go the other way. With Betts, this isn’t happening. He’s not just pulling the ball more — he’s also lifting the ball more. That’s not always so easy to do. Here are year-to-year changes in average launch angle, with Betts being the point in yellow.

Betts was already something of an air-ball hitter, but his average launch angle has increased by 10.7 degrees. That’s the game’s third-biggest increase to this point, with Betts behind only Leonys Martin and Francisco Cervelli. To the pull side, Betts’ historical launch angle was right around 10 degrees. Now it’s up at 20. Betts is pulling the ball, and pulling it in the air, which is exactly what he would need to do in order to maximize his skillset.

Two videos can hardly tell you very much, but just so you can see what this might look like, here’s Betts in Angel Stadium in 2017, swinging at a slider over the plate.

And here’s Betts in Angel Stadium on Tuesday, swinging at a slider over the plate.

I don’t know what the mindset was in the 2017 video, and obviously Betts has hit plenty of homers before, but in the second clip, the intention is readily apparent. You see Betts trying to hit the ball hard. He doesn’t cut his own swing off. He looks like a home-run hitter. Maybe he was just feeling it on Tuesday, I don’t know. But Betts is someone who’s slugging .796, while running a contact rate above 90%. In this era, Betts appears to be poised to put his contact skills to great use.

What can you do, as a pitcher? Betts just isn’t going to strike out very much. He never has, and he never will. It’s understood that Betts is pretty weak when he goes to right field, so, here are the pitches that, in 2017, forced Betts to go the other way:

Unsurprisingly, last year’s Betts wasn’t often able to pull outside pitches. Trying to pull outside pitches is exactly how hitters get themselves in ground-ball trouble. So, in theory, as a pitcher, you just try to work Betts away, but this is where his eye comes in handy. In terms of swinging at pitches over the outer third or beyond, Betts is running one of the very lowest swing rates in the league. He knows his zone and he knows his strengths almost perfectly. Every hitter is capable of occasionally being fooled, but, generally speaking, Betts won’t swing at an outside pitch unless he has to. Until there are two strikes, or unless the situation demands a particular approach, Betts seems happy to look for something to drive to left or left-center. I didn’t plan to pad this post with a comparison between Mookie Betts and Jose Bautista, but this approach is reminiscent of that one. J.D. Martinez is proof of the power of being able to hit the ball hard to all fields, but Betts is proof you don’t have to be able to do it. Not if you know every nook and cranny of the zone.

Betts, of course, won’t finish the season with a batting line that makes him out to be the new Barry Bonds. Yet, there are few things more valuable than a pulled batted ball in the air. Mookie Betts is hitting like he knows it. As the opposition is concerned, these are not going to be easy adjustments to make. Betts never makes anything simple.