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One Big Question: Can Darwinzon Hernandez even up his splits?

He was amazing against lefties. Against righties? Not so much.

Boston Red Sox v Tampa Bay Rays Photo by Julio Aguilar/Getty Images

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 Darwinzon Hernandez.

The Question: Can Darwinzon Hernandez dominate against righties too?

The Red Sox are in a position to make the playoffs his year, though it is far from a sure thing. Depending on who (or what projection system) you ask, they are either the favorite for the second wildcard spot or they are in a very crowded mix on the outside looking in for that spot. The American League is not going to be as top-heavy this year, which means there will be more competition for the lower postseason spots, which in turn means teams in that crowd need more to go right to make the playoffs. For each of these teams, the high-variance players, or X-Factors, or whatever you want to call them, become the focal point.

For the Red Sox, they have a few of those players in each area. While I think the rotation will ultimately tell the story for this team insofar as any position group can lay that claim, the bullpen is an interesting group as well. I tend to believe they are better than they get credit for, but there is plenty of variance there even considering how much variance there always is for every bullpen group. There is legitimate concern about regression from Brandon Workman. Matt Barnes is always something of an unknown. Josh Taylor was really impressive, but you never know how the league will come back in a sophomore year.

Darwinzon Hernandez, though, is the most important pitcher in this bullpen. To me, if the Red Sox relief corps reaches its peak potential, or something close to it, it’s because Hernandez emerged as a true-late inning reliever. There is no doubt he showed flashes last year indicating he can be exactly that, but there are still improvements to be made. Control is the one that is brought up the most often, which makes sense considering he walked just about 18 percent of his opponents. What I want to focus on, however, are his platoon splits.

Boston Red Sox Spring Training Workout Photo by Billie Weiss/Boston Red Sox/Getty Images

Overall, it was a good first taste of the majors for the young southpaw, who tossed a total of 30 13 innings in the majors last season and pitched to a 4.45 ERA with a 2.78 FIP and a 3.04 DRA. Obviously, the sample with which we are dealing is not big, which means the platoon splits are even smaller. Still, it is worth noting that while Hernandez held fellow lefties to a tiny .202 wOBA (on the same scale as OBP), righties put up a huge .404 number. For a little more context, that wOBA against lefties was the ninth lowest among 503 pitchers who recorded at least 30 outs against them while the wOBA against righties was 52nd highest among 576 pitchers. That’s a massive gap, and if he is going to be a true late-inning arm he needs to be able to pitch against anyone.

My first thought here was to look at potential bad luck, particularly considering the size of the sample. He did indeed allow a .476 batting average on balls in play against righties compared to a .286 mark against lefties. The former will not stay that high over a more reasonable sample. That said, it was worth digging a little deeper into the batted ball numbers. The good news is he actually allowed hard-hit contact at a lower rate, per FanGraphs. The bad news is he didn’t allow much soft contact against righties either, something he was elite at against lefties. Furthermore, both his fastball and his slider — his two main offerings — had higher expected wOBAs and much higher actual wOBAs. It is worth noting that his expected wOBA lagged way more behind the actual mark against righties than it did against lefties. So, there was some bad luck here as well as some real issues, particularly with the soft contact.

Beyond the contact profiles, though, the strikeout rate is actually what is more concerning. This surprised me because it seemed like Hernandez was striking everyone out. It wasn’t that he was bad against righties — his strikeout rate of 28 percent against them is still very good — but that he was otherworldly against lefties with a rate above 56 percent. With his walk rate, though, he needs to be otherworldly. Here, the slider was about as effective at inducing whiffs against hitters of either handedness. The fastball, on the other hand, had a whiff rate of 48 percent against lefties versus a rate of 30 percent against righties. That’s an issue for a pitch he throws three quarters of the time. Some of that will be born out in the zone plots below.

vs LHH; via Baseball Savant
vs RHH; via Baseball Savant

There’s a couple of things that stand out here. for one thing, he owned the top of the strike zone against lefties, but his glove side just wasn’t there against righties. Part of that is the fact that his slider breaks away from righties there, making it easier to get whiffs on that side of the plate. However, it was clearly easier to hit his fastball as it was coming in towards the batter. Just look at the whiff rates in the zone. Hernandez could blow anything by lefties, but righties just weren’t swinging through much of anything in the bottom two-thirds in the zone.

It’s hard to get a great read on Hernandez given, again, the small sample size. That said, there are big expectations here, particularly if Workman regresses more than the team is expecting. Now, I do think they will mitigate some of these platoon issues by using him as an opener against lineups with a bunch of lefties at the top, but the ultimate goal needs to be to get him in the late innings pitching against anyone. It’s worth noting his splits in the minors bounced all over the place, but that was also as a starter which is a totally different beast. I think it would serve him well to throw his slider a bit more to try and get some more whiffs in the zone and keep the opponents off-balance. Whatever the solution, this is the area on which I’ll be most focused for Hernandez in 2020.