What the Yankees should consider before trading for a pitcher

It’s trade season and everyone has a different take on who the Yankees should deal for. Do you target the former postseason hero who until recently was on a steady decline? Or do you focus on the groundball machine within your own division? We all know the Yankees could really use one more starting pitcher, but which particular pitcher is often cause for consternation.

One of the other areas we often discuss is the impact of moving into Yankee Stadium, one of the better hitter’s ballparks in the game. Even though YSIII ranks near the bottom in this year’s one-year park factors, three-year averages put the Stadium comfortably among the top quartile of hitters’ parks.

With that in mind, I think it’s useful to investigate what kind of pitchers are actually hurt by playing in the Bronx - does a particular kind of contact hurt you more than another, specifically at Yankee Stadium? Fortunately, we can pull the performance of every single Yankee pitcher who has appeared at Yankee Stadium since it opened, and test what correlates most with their ERA:

Strikeout rate, groundball rate and soft contact have the highest negative correlations with ERA, meaning that the higher your three rate stats are, the lower your ERA. Meanwhile, Yankee Stadium appears to not be so kind to surrendering line drives.

Really though, in order to better analyze this we need to understand how generic MLB ballparks reward or penalize these kind of rate stats. So, lets look at how every MLB pitcher since 2009 has done with these same correlation coefficients:

So this really gives us a different look - Yankee Stadium may surrender more runs overall than the generic MLB ballpark, but there’s not much that has particularly hurt more at YSIII. Groundballs are just as valuable in the Bronx as elsewhere, and hard hit balls will hurt you just the same no matter where you’re playing.

Two things stick out - walk rate and line drive rate. Walks contribute far less to overall runs allowed at YSIII than in MLB writ large, and this is fascinating to me. A lack of control in a hitter’s ballpark means you’re more likely to overcompensate, or that when you give up an extra-base hit, you’re more likely to have men on for it. And yet that doesn’t seem to be the case.

I think the cause of that is mostly the stature of the Yankee bullpen. First of all, as a starter, once you lose the strike zone you’re taken out and a high-octane reliever is brought in. Think about the 2017 Wild Card game as one example, and there are plenty of others that are not as extreme. In this case, the starter’s high walk total may not hurt him as much as you’d think by the raw stats, since the reliever is capable of saving the day.

A second, related explanation is the Yankee bullpen itself. There are a lot of guys in the Yankee ‘pen that effectively suppress runs while also walking more guys than you’d like, all else equal. Dellin Betances, Adam Ottavino and Zack Britton have always had less-than-ideal walk rates, despite being among the best relievers in the game. All in all, of the 31 relievers to throw at least 50 innings for the Yankees since 2009, 14 of them were above that 3.50 BB/9 benchmark that would be considered “normal” control for a reliever. Of course, 14 relievers of the 31 also struck out more than a batter per inning, lowering the risk of walks to a certain extent.

What this should tell us is that walk rate isn’t as crucial at Yankee Stadium as it might be elsewhere - or perhaps more accurately, it isn’t as crucial on the Yankees as it might be for other teams.

Now, if we look at line drive rate, we see the exact opposite. Here, line drives actually hurt you more than on the MLB on average, and this is completely because of the ballpark. Let’s look at the short porch in right, 314 feet away with an 8 foot wall. That’s the shortest part of the park, both in terms of wall height and distance from the plate.

Back of the envelope trigonometry - also the name of my high school punk band - tells us that a hard line drive then needs to be about 14.5 degrees off the ground to clear the right field wall. Sure enough, when we pull the Statcast data on all the home runs hit at Yankee Stadium since 2015 - the first year we have data - the lowest launch angle on a home run at the ballpark is 15 degrees!

Compare that to another good hitter’s park, Rogers Centre in Toronto, where the shortest distance is a 10 foot wall, 330 feet from home plate. This time, the lowest launch angle to ever produce a home run is 17 degrees. Two degrees isn’t that much, sure, but it shows that you don’t need to loft the ball as much at Yankee Stadium as you do elsewhere, and so pitchers who give up line drives have a much higher risk floor.

I’m not here to propose a trade target. If you read my work, you know that there are particular pitchers I think would be good fits for the Yankees, and ones who aren’t. All I want to point out is that groundballs and fly balls aren’t inherently better or worse for guys who pitch on the Yankees. The things that really do hurt you more at Yankee Stadium aren’t what you expect, and that’s food for thought in all our trade talks.