Why did the Yankees struggle against the Orioles in 2018?

One of the most annoying things about the Yankees’ 2018 season was their struggles against the lowly Baltimore Orioles. Perhaps “struggles” is a bit dramatic, considering the Yankees’ 12-7 head-to-head record with a +34 run differential against the O’s. Yet the Yankees won 100 games and the Orioles won less than half of that. It would have been nice to see a more lopsided record. Like, say, the Red Sox’ 16-3 mark against Baltimore.

Common sense dictates that the Yankees going 12-7 instead of 16-3 against the Orioles is just another random occurrence in a sport chock full of them. Normally, I’d agree and move on. However, it’s the offseason, which allows for the time to take a deeper dive into the numbers. As it turns out, there may be more to the Yankees’ underwhelming record against the Orioles than randomness or luck.

Consider the Yankees’ offensive performance against the O’s. The Bombers as a team hit .274/.354/.455 against Baltimore, for an OPS of .808. That’s a very good batting line, but when you compare the Yankees’ offensive performance to how other teams fared against the O’s, the Yankees’ slash line doesn’t really stand out.

Let’s see how other divisional rivals hit against the Orioles. The Red Sox, for example, clobbered Baltimore’s pitching to the tune of a .295/.378/.542 line (.920 OPS). The Rays (.827) and Blue Jays (.839) enjoyed facing the Orioles as well, to a somewhat lesser degree. Within the AL East, the Yankees actually did the worst offensively when facing Baltimore, despite having the highest overall team wRC+ of them all.

The Yankees’ hitting against the O’s was mediocre when compared against all of MLB as well. Baseball Reference features a stat called sOPS+, which shows how well a team did in a particular split compared to the MLB’s overall performance in that split. In this case, it tells us whether the Yankees’ OPS against Baltimore was better or worse compared to how Baltimore fared against opposing batters overall. Sure enough, the Yankees’ .808 OPS was only good for a 98 sOPS+, which means that the Yankees were slightly worse than average when facing the Orioles.

This trend of underperformance can be observed in the Yankees’ pitching against Baltimore as well. Overall, the Orioles had a team batting line of .239/.298/.391 (.689 OPS). When facing the Yankees, though, Baltimore’s bats rallied to hit .252/.312/.418 for a .730 OPS. So we’ve established that the Yankees’ 12-7 record against the Orioles this year wasn’t a case of poor run sequencing - the Yankees’ bats and arms both legitimately played worse against Baltimore.

Of course, it’s important to not read too much into this observed underperformance, as we’re talking about a 19-game sample size here. Still, there is a likely culprit for this phenomenon - namely, the penalty that fly ball hitters endure when facing fly ball pitchers, and the boost that groundball hitters enjoy when facing fly ball pitchers.

The effect described above was named the “trajectory platoon” and demonstrated pretty thoroughly by Shane Tourtellotte in an article for the Hardball Times in 2015. Looking at the top 10 percent of both groundball and fly ball hitters in 2013-2014, Tourtellotte found that batters in both cohorts produced elevated line-drive rates when facing pitchers of the opposite cohort - fly ball hitters against groundball pitchers, and vice versa.

Since line drives are the type of contact most conducive to hits and runs, this helps the batter. On the other hand, pitchers facing hitters or the same batted ball type cohort can generate his preferred contact type, be they fly balls or ground balls, at an extreme rate, while depressing line drive rates. Advantage: pitcher.

Returning our focus to the Yankees-O’s matchup, we indeed find that the trajectory platoon is at work here. The Yankees’ offense owned the sixth-lowest groundball/fly ball ratio in MLB in 2018. Sure enough, they ran a 99 tOPS+ against fly ball pitchers in general. Meanwhile, the Orioles’ pitching staff also owned the sixth-lowest GB/FB ratio in baseball. Yankees versus Orioles equates to fly ball hitters against fly ball pitchers.

The same can be said for the O’s hitting performance against the Yankees, as the O’s had a GB rate of 44.1 % (11th-highest in MLB) while the Yankees’ arms collectively owned a middling 35.1% fly ball rate. The trajectory platoon was somewhat in the O’s favor, which may have contributed to their offensive overperformance against the Yankees.

It looks like the Yankees’ underwhelming performance against the O’s might have been due to their batted ball tendencies, both in terms of hitting and pitching. How big is this issue? It’s certainly not ideal, but we’re also talking about a matchup that a) the Yankees went 12-7 in, and b) the difference in talent level between the two clubs is large enough to overcome any platoon disadvantage that the Yankees face. Offensively, “try to hit more line drives” is always good advice, but that’s what the Yankees (like everyone else) are trying to do - they just like to err on the side of fly balls. However, if more clubs start taking advantage of the trajectory platoon, then the Yankees just might have a problem.