Having a lefty-heavy rotation doesn’t really matter

The Red Sox are, uh, in flux right now, what with not having a manager in the middle of January, not to mention major questions regarding significant players like Mookie Betts, David Price and Jackie Bradley Jr. There is a lot of work to be done (or not done!) between now and mid-February when spring training gets underway. All of that stuff is, of course, the focus for the front office. For our purposes, though, we can’t solely focus on that stuff, both because I would lose my mind and also because I just don’t have anything new to say. So, we turn our attention to the current roster as it stands right now.

It goes without saying that we’re not exactly sure how the roster is going to shake out by the time the actual games start. Specifically, we don’t know what the rotation is going to look like. The David Price trade rumors have seemingly slowed down of late, but it seems likely it’s still something they’re at least open to. Either way, we have a pretty good idea that at least four-fifths of the rotation will be Chris Sale, Eduardo Rodriguez, Nathan Eovaldi and Martín Pérez. Price is a question mark. One thing that stands out there is that at least three of those pitchers are lefties, and if Price isn’t dealt that would leave them with four southpaws. Some people have suggested this could be an issue, but is it really?

There are a few different ways to tackle this question. The first one is to look at some history and see if lefty-heavy rotations have had any more or any less success than your typical rotation. To do this, I looked at the three rotations with the most innings from left-handed pitchers in each of the last five years — so, a total of fifteen teams for all my math heads out there — and checked their overall rotation’s ranking in ERA and wOBA against. This is far from a scientific method, as we’re not controlling for park effects or American League versus National League or a ratio of total innings from a rotation, but as quick, back-of-napkin work it works fine as a baseline. The results are below.

This is pretty much inconclusive. Judging by these — again, unscientific — numbers, there’s really no correlation, which makes sense. My hypothesis was that handedness doesn’t matter as much as, you know, how good the pitchers are. The Dodgers are on this list a lot, for example, and always ranked highly because they had Clayton Kershaw the whole time plus guys like Hyun-Jin Ryu, Rich Hill and Alex Wood, among others. The Red Sox had two wildly different results, not because of any different disadvantage but rather because the pitchers just weren’t as good in 2019 as they were in 2018.

So, if it’s about the quality of the pitchers, we should probably look at the Red Sox pitchers! Specifically, we should consider if they are easily beaten by loading up with right-handed hitters, which is presumably the issue with having a lot of lefties. Below, we have another table, this time showing all four of the lefties currently in the rotation. For each pitcher, we look at their wOBA difference between righties and lefties from last season as well as the last three years combined. A positive number means they were better against righties and a negative means they were better against lefties.

The takeaways here? Well, for one thing, Eduardo Rodriguez actually prefers to face right-handed batters. That is not terribly surprising considering his best pitch is often his changeup, which is a pitch that generally works better against opposite-handed hitters. Sale and Price, meanwhile, have some split but nothing too significant. It also should be mentioned that they were still good against both — particularly Sale in the three-year measure — just a little worse against lefties. Pérez is the big issue here, but it is less of an issue for him if the rest of the rotation pitches up to their potential. As long as that happens, the bullpen should be fresh enough to allow whoever the manager is to use Pérez for short starts.

The final piece of the puzzle is the competition. Are the teams the Red Sox are going to need to worry about built particularly well to beat up on left-handed pitching? This is where things start to get a little less optimistic. Looking at the competition around the American League, there are a lot of good right-handed hitters. The Yankees and Astros are both absolutely loaded with right-handed thump. The Twins are a little more balanced, but they have Nelson Cruz and just added Josh Donaldson, making for a terrifying 1-2 punch in the middle of that order. They can also just plain hit, no matter who is on the mound. The Rays have a lineup that is basically built to platoon all over the diamond. The Blue Jays have young talent in Bo Bichette, Vlad Guerrero Jr. and Lourdes Gurriel all at the top of the lineup. The A’s have Marcus Semien, Matt Chapman, Khris Davis and Mark Canha. The Angels have a guy named Mike Trout as well as Anthony Rendon and Justin Upton. The point: There are a lot of righties who can beat up on lefties.

So, where do we land with all of this? Ultimately, it still simply comes down to getting the best pitchers without worrying about handedness. In other words, casting financials aside if there is a decision between trading Price or Eovaldi, they shouldn’t favor the latter just because he’s a righty. Price is better, and that is what matters more. As far as the scenario in which they trade Price and need to find a replacement, they shouldn’t be worried about it being a lefty if that’s the best option. The right-handed competition in the American League is certainly concerning, but handedness should really only come into play as something of a tiebreaker.