Why have the Yankees pitched worse with the shift?

Earlier this week, I took a look at whether the Yankees were shifting too much. To summarize my findings: the Yankees have shifted more than any team other than the Astros in 2018, but their pitchers put up significantly worse numbers with the shift on than without. The Yankees pitchers drop in performance with the shift on was the second-largest in the league, behind only the Mariners.

That, obviously, is a bit problematic from a strategic standpoint. The whole point of the shift is that it is supposed to help the shifting team prevent runs. By putting the shift on, though, the Yankees seem to be generating much worse results from their pitchers.

The question I’m interested in now is as to why this is happening. The shift is generally good at taking groundballs and turning them into outs, so why are the Yankees so much worse when they shift? What is causing their numbers to inflate when they move their infielders around?

In my last piece I referenced the excellent work of Baseball Prospectus’ Russell Carleton and ESPN’s Sam Miller. I encourage you again to read through their findings, as they are thorough and fascinating. At BP, Carleton’s research of the shift suggests that pitchers as a whole pitch worse when the shift is on, mostly by throwing more balls. More balls obviously means more walks, as well as more hitter’s counts, which leads for more opportunities for hitters to do damage with extra-base hits.

Exactly why pitchers struggle with getting the ball into the zone while the shift is on is a compelling question. My personal (amateurish) intuition is that all the pitchers that initially complained when use of the shift was expanding, those that thought it garish, uncomfortable, strange, were onto something. The simple feeling of unease those pitchers encountered when wide swaths of space were opened up behind them, spaces that until recently were covered, might have led those pitchers, consciously or not, to pitch a little bit worse when the shift is on.

For now, it’s impossible to tell what psychological reason could be causing pitchers to miss the zone more when the shift is on. Returning to the Yankees: is an increase in walks and balls driving the team’s poor pitching with the shift on?

Curiously, what Carleton found to drive the league-wide drop in performance with the shift doesn’t seem to hold in the specific case of the Yankees. Using Baseball Savant, I looked at the rate at which the Yankees pitched in the zone with the shift on, and without. Without the shift, they hit the zone 47.7% of the time. With the shift? That figure actually bumped up to 49.0%.

No, the Yankees have pitched worse in other ways. Without the shift, Yankees pitchers have generated whiffs on 26.4% of swings. That figure falls to 24.1% with the shift on, suggesting that opposing hitters have had a slightly easier time making contact when the Yankees put the shift on.

It also appears as though opposing hitters not only found more contact against the shift, but better contact as well. The Yankees have almost exactly the same exit velocity with the shift on, but have allowed a higher average launch angle by over one degree with the shift on. Their groundball rate without the shift is 44.6%, but that rate falls to 43.4% with the shift.

That better contact adds up to a 30-point increase in slugging for opposing hitters: the Yankees have allowed a .371 slugging percentage without the shift but a .401 mark with it. So, while the Yankees haven’t lost their control with the shift on, something about the shift seems to be causing them to yield more damaging contact.

It seems we’ve answered the why when it comes to the Yankees’ worse performance with the shift: more contact and better contact. What’s harder to answer is the how. There is probably a confluence of small factors combining to push the Yankees to worse results with the shift, none of them easy to pin down. Maybe the pitcher misses his spot by an inch or two more, helping the hitter square it up. Maybe the pitcher doesn’t quite spin that sharp slider just right, causing it to be a little less sharp, allowing the hitter to catch up to it in a way he couldn’t previously.

Regardless, the Yankees’ aggressive use of the shift still doesn’t look like a great idea. They generate fewer whiffs and fewer groundballs, giving opposing hitters a small but significant boost. The shift may look smart on paper, but in practice, it seems to be hurting the Yankees more than it is helping.