The Change: Figuring Out The Home Run Rates

Once upon a time, strikeouts minus walks was the best way to look ahead for a pitcher. It focused on the things that a pitcher could control and left the rest to league averages, and therefore it was a strong ‘one number’ to look at.

We are in the midst of turmoil, though. In the middle of the biggest year to year increase in home run rate, we’re suddenly looking at pitchers with home run problems and wondering which ones will continue to be ridiculously ‘unlucky’ and which ones will shortly conquer their gopher problem. Don’t worry, the pitchers themselves are doing the same thing.

The good news is that we have new tools to help us figure out which home run rates are more likely to regress. The home run is the result of the correct launch angle and the correct velocity. We know that 25-30 is the ideal home run launch angle, but for these purposes, I expanded it to 20-35 to get a broader range. We also know that 95+ mph in those zones leads to home runs, so I included a ranking of exit velocity in that band.

The leaderboard below shows the bottom 20 starters in home runs per nine, and where they rank in exit velocity and percentage of balls in play in the power launch angles. What we are looking for are guys that are giving up home runs but aren’t really bad at allowing balls in the right angles at the right velocities.

Chris Young looks like he utterly deserves his home run rate. Only 12 pitchers in the sample gave up more pitches in the power launch angles, and only two are allowing those balls to exit at a higher velocity. It’s a poisonous cocktail he’s serving, and Erik Johnson and Tyrell Jenkins are right there with him. Thanks to Brian Cartwright, we can see what Young’s launch angles look like visually:

But there are a few (young) pitchers that jump out on this leaderboard. Let’s take a look at them.

Dylan Bundy
Maybe this is just a small sample thing, since Bundy has allowed only 33 balls in play in the power launch angles. But 50 balls in play tell us a great deal about a hitter’s exit velo, so those 33 balls contain some signal. And so far, those balls have average 89.5 mph, which is almost two mph below average and good for 36th-best on the list. Armed currently with a rising 94 mph fastball, a split-finger getting 25% whiffs, and a damage-limiting curve, he has the pieces to succeed and is an interesting pickup in deeper leagues.

Cody Reed
This spring, when I was talking to Joey Votto about the young pitchers in camp, he asked me if I’d seen Cody Reed pitch yet. Here, we have an even smaller sample, but it might be good news now. Because Reed can keep the ball down (67th in angles), but has allowed those 16 balls in play at a whopping 96.2 mph velocity that of course has led to home runs. His slider hasn’t given up a home run, the change isn’t the problem, and there’s no reason, other than early career noob-ness, that his 93 mph fastball should give up this many homers. He’s a buy in all dynasty leagues.

Eduardo Rodriguez
From a per pitch perspective, there’s still a lot of reason to like Rodriguez. His change has a ton of movement and gets whiffs all the time. His fastball, at 93, is plus for a lefty. Now he’s throwing a harder slider which may bring it all together. From a home run perspective, he gives up a ton of fly balls (195th in angles), but they are mostly soft (89.8 mph). He’s been more ground-ball heavy in the past, too. Rodriguez just isn’t this bad, and is a good pickup in deeper dynasty leagues.

Luis Severino
He’s back! But he’s in the bullpen. And some of the shine has come off of Severino since he was the dazzling, high-velocity Yankee wunderkind. He’s still on 22, but he hasn’t shown us a reliable secondary pitch. The change is average and the slider is inconsistent. This year, his 94.4 mph exit velo was really bad (186th), but he was limiting the angles (21st), and it was only 17 balls in play. Like Reed, we’re hoping the next fly balls aren’t as hard. Like Reed, he’s a buy-low in all keeper leagues.

Down table are a few bigger names. Drew Smyly is actually 37th in exit velo despite giving up tons of balls in the power angles, so he’s a little unlucky. Mike Foltynewicz is average in angles and better than average on exit velo, so a 1.75 HR/9 is a little ridiculous.

Nathan Eovaldi, on the other hand, is not great at limiting those angles (149th) or limiting the velocity (138th). I wouldn’t expect his homer rate to go down much. Michael Pineda is below average at limiting angles (117th) and velocity (179th), too. Be careful with the two Yankees.

The biggest young sleeper based on this research may be Carlos Rodon. He’s 45th in limiting power launch angles, and 15th in exit velo in those bands (88.4), and yet he’s given up 1.47 home runs per nine. That won’t happen any more going forward. Best vet sleeper goes to Scott Kazmir, third in angles and 23rd in velo with a 1.4 HR/9.

Not all home rates are the same! Use the search on BaseballSavant.mlb.com to find a pitchers’ percentage of pitches in the power launch angles (sample median was 3.26), and their exit velo on those pitches (sample median was 91.4 mph), and you’ll have a sense of their ability to improve their results on homers.