Going Deep: Something is Off with Mookie Betts

Mookie Betts has had an inconsistent 2019 season. Matt Wallach takes a look at what is odd about Betts' season thus far and if he can turn it around.

One of the biggest surprises from the first half of the season is the surprisingly weak offensive performance of Mookie Betts. Betts’ 2018 season was superb in every sense. Coming off of what was his worst season as a full-time regular in 2017, Betts redeveloped himself and began hitting the ball harder and at one of the highest rates in the league, hitting fewer groundballs and began pulling the ball at the highest rate of his career. Setting career highs in ISO and wOBA, he won the MVP award, posting 10.4 fWAR, accumulated by combining his strong defensive prowess with those major improvements in his offensive game. To top off what was already a great season, the Red Sox won the World Series in dominating fashion, and things were looking good for Mookie Betts.

Fast forward to 2019 and Betts is seen as a consensus top pick in fantasy drafts, with sky-high expectations to be a good consolation prize for those who were not fortunate enough to land Mike Trout. Expecting Betts to repeat his 2018 performance is maybe asking for too much, but he was definitely expected to be the top bat on most fantasy teams. Early on, he was rewarding owners with a .921 OPS in March and April combined, which may seem underwhelming compared to his 2018 performance, but all told, it’s hard to be upset with a .381 wOBA and .232 ISO to kick off the season. Once the calendar flipped to May though, Betts’ performance started to slip and he’s been a much different player. Here’s a look at Betts’ March and April compared to his May and June:

March/April 132 13.6 14.4 .295 .394 .527 .921 .232 .381 136
May/June 256 17.2 15.2 .243 .375 .414 .789 .171 .342 110

We see that other than improvements in his walk-rate, Betts has been an entirely different hitter since the end of April. The power decrease is really concerning as he went from slugging like Rhys Hoskins or Gleyber Torres to slugging more like Amed Rosario or Brandon Belt. Thankfully, Betts still had his elite plate discipline to prop his numbers up, as it would look pretty ugly if he didn’t. You could say that if it weren’t for the shocking struggles of Jose Ramirez, we may very well be talking about Mookie Betts being the biggest disappointment of 2019 fantasy first-rounders. Something is definitely off with Mookie, and I wanted to figure out what it was.


A Reverse Split


I believe the biggest thing that stands out about Mookie Betts in 2019 are his numbers against left-handed pitching. I will admit that when I first looked at his splits against lefties, I was so baffled I had to double-check to see if I was looking at the right player and split. Turns out my eyes were indeed correct, and I did confirm that I was looking at 2019 Betts. See for yourself:

Aside from 2016, Betts has always been better against left-handed pitching, and especially so during his MVP 2018 season. It’s not like this is a minor difference in wOBA either, as his .488 wOBA against left-handers has dropped all the way to .276 this year. His drastic declines against lefties aren’t just in wOBA, as we can see in the following table:

Season PA BB% K% AVG OBP SLG OPS ISO wOBA wRC+ Oppo% Hard%
2018 155 17.4 13.5 .368 .471 .736 1.207 .368 .488 212 20.6 45.8
2019 104 15.4 11.5 .216 .337 .307 .643 .091 .276 65 29.0 33.3

Now you see why I was so shocked when I first saw this. That’s a 147 point drop in wRC+ against left-handers from just one season to the next. A right-handed hitter doesn’t just lose this much production against the more favorable platoon split on accident, there has to be more to it.

Indeed, I did find something that maybe explains the huge drop-off. Take a look at where Betts was seeing pitches and his results against left-handers in 2018:

Against left-handed pitchers in 2018, Betts was getting pitched to as right-handed hitters are usually pitched to: away. He was seeing the majority of pitches on the outside portion of the strike zone. Unlike most right-handed hitters, Betts did most of his damage on those outside pitches and his weakest spot was on the inside portion of the zone. Now compare those 2018 charts to 2019:

We see that pitchers have been adjusting to how they pitch to Betts, as he is generally seeing fewer pitches on the outside portion of the strike zone and more pitches being thrown in his more troublesome areas from 2018 and what we get is less slugging all-around. Another takeaway is the increased rate of batted balls going the opposite way. We saw earlier that a lot of Betts’ 2018 success can be attributed to pulling the ball more, as more pull usually means more power. Betts is being pitched more to the inside portion of the plate but is putting more of those pitches in play to the opposite field. When Betts goes the other way against left-handed pitching, he is slugging .250 compared to a substantially better .533 mark when he goes to the pull side against lefties. While that .533 mark is still lower than his slugging against lefties in 2018, it is definitely more desirable than the .250 mark he has put up when he goes to the opposite field.


Regression to the Mean?


The struggles against left-handed pitching cannot possibly be the only thing causing Mookie Betts‘ down 2019 season, as only 25% of all the pitches he’s seen have come from the arms of left-handed pitchers. Another area that Betts is noticeably weaker from 2018 is against breaking and off-speed pitches. Remember, everything seemed to go right for Betts last season, and that appears to include his performance against those non-fastball pitches. Here are Mookie Betts‘ average performances (excluding 2018) against breaking and offspeed pitches going back to 2015 compared to his 2018 and 2019 figures:

Season / Pitch Type BA xBA SLG xSLG wOBA xwOBA
Breaking 2018 .275 .247 .557 .442 .383 .342
Offspeed 2018 .347 .283 .680 .531 .452 .392
Breaking 2019 .296 .253 .449 .407 .348 .332
Offspeed 2019 .286 .290 .449 .405 .339 .329
Average Breaking (excluding 2018) .292 .252 .458 .364 .336 .295
Average Offspeed (excluding 2018) .316 .283 .473 .407 .358 .322

We see here how much 2018 stands out, and one could say that Betts maybe got a little lucky in 2018, as his actual stats outpaced his expected ones and that his 2019 numbers are more in line with his career averages. Betts has a combined .406 xSLG on breaking and offspeed pitches in 2019, which puts him just inside the top-100 at 99th among 394 hitters who have seen at least 300 pitches, so while Betts is still better than most of his peers, keep in mind that he was top-20 in this same statistic a year ago. So, while Betts is still better than average against breaking and offspeed pitches, he has seen a regression back towards his previous career averages.

Evaluating the 2019 season of Mookie Betts is tough. He’s still been a good player all things considered, and there aren’t many players where a 124 wRC+ would be considered a disappointment, but considering the type of season he had only a year ago, you would probably be underwhelmed by Betts this season. One thing that should be mentioned is that if you believe in small samples, Betts has been much better in his thirty plate appearances in July, with a 1.186 OPS in six games before the All-Star break. We would need to see a stretch like that last for a bit longer than six games before we fully buy back in, but Betts has talked a lot about making adjustments and putting extra work in lately to get himself back to that level that he knows he can reach.

Betts must continue to make adjustments—his performance against left-handed pitchers should be at the top of the list—but we all know what type of player Betts can be when he is at the top of his game. While I may be a Yankee fan, I am also a fan of baseball. Having a star like Mookie Betts is ultimately good for baseball, and having him produce like one of the best players on the planet is even better for the game, so I am rooting for Betts to turn it around. As for now, things are just off for Mookie Betts, but I do believe that he can turn it around. Getting 2018-level Betts back for the second half would be a much-needed boost to an inconsistent Red Sox team and get them going in a season that has been a sharp contrast from their dominant 2018.

Featured Image courtesy of Nick Wosika/Icon Sportswire.

Matt Wallach

Matt studied accounting at UAlbany, is a Yankee fan, and writes for Pitcher List and Rotoballer where he can work with even more numbers to analyze baseball players, which is a lot more fun.

One response to “Going Deep: Something is Off with Mookie Betts”

  1. Mark says:

    If you look at his career stats, last year was the outlier not this year. He had a career year last year. When compared with previous generations of ballplayers and looking over his career stats he’s probably not HoF caliber. On the bubble at best. Of course there are so many MLB players nowadays that wouldn’t even make it to AAA ball in the past. So relatively speaking, maybe he will make the HoF someday.

    As a lifelong Sox fan, I truly hope that 2018 becomes the norm for Mookie, but I doubt it.

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