One Big Question: Can Rafael Devers make a leap against lefties?

Welcome to Over the Monster’s One Big Question series. For those unfamiliar, this is something of a season roster preview where over the next 40(ish) (week)days we’ll be taking a look at each player on the 40-man roster prior to the season. If changes are made to the roster between now and Opening Day, we’ll cover the newly added players. Rather than previewing what to expect in a general sense, the goal of this series is to find one singular question — sometimes specific, other times more general — for each player heading into the coming season. We’ll go alphabetically one by one straight down the roster, and you can catch up with the series here. Today, we cover Rafael Devers.

The Question: Can Rafael Devers reach another level against lefties?

In the terrible season that was 2019 in which so many things went wrong, Rafael Devers emerged as the story of the year, at least from a positive perspective. He had a breakout in every sense of the word, making good on so much of the potential we saw from him in the minors and turning into a real, star-caliber player. By the end of the year he had smacked 32 homers and hit .311/.361/.555 for a 132 wRC+, putting him 30th on the wRC+ leaderboard among all qualified hitters. Throw in the improved defensive work at third base, and 2019 was about all we could have asked from Devers.

The scary thing for the rest of the league is that there is still another level that can be reached by the now-23-year-old. Devers was an All-Star caliber player last year, finishing the year worth just under six wins above replacement by FanGraphs’ measurement, if that’s your thing. There’s still another level to be unlocked to make him MVP caliber and a real superstar in this league, though it’s far from a guarantee he’ll ever get there. Many players have potential to reach that level, but few do on a consistent basis. Devers could get there by improving his plate discipline, and in particular upping his walk rate, but that’s not really his style of hitting. I can see him maybe getting up to around eight percent with the walk rate, but a substantial leap seems to be less likely.

In my estimation, the more logical path for Devers to build off his 2019 would be to improve against lefties. For as great as he was overall last year, he struggled against same-handed pitchers, perhaps even moreso than the overall numbers would indicate. On the year, he hit .269/.301/.442 against southpaws for an 89 wRC+ over 208 plate appearances. Over his career, he has a 95 wRC+. Those aren’t unplayable, must-be-in-a-platoon numbers, but if he wants to be the superstar he really can be, this is where the improvement should come.

My first instinct in seeing these numbers were that this must come down largely to struggles against the breaking ball. It would make sense because A) I more vividly remember him struggling against breaking stuff than any other type of offering, B) lefties will throw more breaking balls to other lefties and C) he walked less than three percent of the time against southpaws, a sign that he was swinging at pitches out of the zone. Breaking balls are more likely to be out of the zone.

Sure enough, he did struggle against the breaking ball from lefties. He whiffed just over a quarter of the time against these offerings and put up an expected wOBA of .247 and an actual wOBA of .262, per Baseball Savant. For comparison, against righties’ breaking balls his whiff rate was only a percentage point lower but his expected and actual wOBAs were .352 and .405, respectively.

What really stood out to me as I dug a little deeper, though, was how much he struggled against fastballs from lefties. Against righties, Devers absolutely mashed fastballs in 2019, putting up an expected wOBA of .390 and an actual wOBA of .396. Against lefties, those numbers fell fairly significantly to .337 and .349, respectively. More striking was how hard he was hitting the ball against righties compared to lefties. We all know exit velocity and just hard contact in general was a calling card for Devers all year — he led the league in balls hit over 95 mph and was 14th in average exit velocity — but that surprisingly wasn’t the case against lefties’ fastballs. Below you will see Devers’ average exit velocity by where the pitch was in the strike zone against lefties and against righties. Note the differences particularly on pitches inside and also up.

That is a start difference, and it goes a long way to explaining his .173 Isolated Power (SLG - AVG) against lefties compared to his .278 mark against righties. And to me, the fastball performance is what is going to make the difference here. I don’t know if it’s a mechanical thing — maybe he needs to shift his stance a bit to better recognize heat coming out of a lefty’s hand? — or a mental thing or what, but it can make all the difference in the world. If he can perform against fastballs and lay off a few more of those breaking balls from lefties — easier said than done, of course — he can get that wRC+ up to about thee 105-115 range. If that’s combined with what he did against righties last year, then we’re talking about something damn close to a ceiling performance from Devers, and a guy who really can compete for MVP awards.