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One Big Question: Can Nathan Eovaldi keep throwing strikes?

Pretty straight forward this time around!

Baltimore Orioles v Boston Red Sox Photo by Adam Glanzman/Getty Images

Welcome to the annual Over The Monster One Big Question season preview series. Over the next 40(ish) days, we will be running through every player on the 40-man roster and identifying a key question for them pertaining to the coming season. This should run us up to the start of the season, at least as it is scheduled now. We will go through the roster in alphabetical order. For the most part, these will run Monday through Friday every week running up to the week before Opening Day, though expect some weekend posts mixed in as well as the 40-man is expected to continue to be altered before the start of the season. You can catch up with every post by following this link. Today we take a look at Nathan Eovaldi.

The Question: Can Nathan Eovaldi pound the strike zone?

There’s very little question that the key to the 2021 Red Sox season is their starting pitching. That is the same old story as pretty much every year, of course, but it seems even more so this year. I’m not particularly optimistic about their playoff chances, but I do see a path and it involves their top three pitchers to start the year being healthy and effective for basically the entire season. A lot of the focus has, understandably, been on Eduardo Rodriguez in his comeback from myocarditis, and Garrett Richards, who just joined the team.

I think that has led to Nathan Eovaldi flying a bit under the radar, though, which is strange because he may be even more important. In what was a lost season in which many people justifiably tuned out last summer, Eovaldi was better than you may have thought. And I think there’s actually a pretty decent chance, if he stays healthy, that he’s the best pitcher on the Red Sox this coming season. But with that said, that itself is far from a sure thing because there is a whole lot of variance with his performance. For some pitchers there is a lot of nuance to figure out the difference between good and bad. Eovaldi isn’t so simple that there’s just one thing standing in the way, but there is one thing that sticks out like a sore thumb. That’s simply throwing strikes.

After undergoing Tommy John a few years ago, Eovaldi has been back on the mound at least sporadically for each of the last three years, and it’s been a rollercoaster. 2018 was good. We know the playoff story, but even in that regular season he put up a 90 ERA- (meaning he was 10 percent better than league-average after adjusting for park) and an 87 FIP-. 2019 was bad. He ended up pitching out of the bullpen after an injury and finished with a 124 ERA- and a 130 FIP-. 2020 was injury-shortened as well as just shortened for everybody, but in the small sample he was good again with an 81 ERA- and 88 FIP-. So two out of three. Not bad.

As he looks to make it three out of four, there is one really big difference that is impossible to ignore between his two good seasons and the one bad one. In 2018, Eovaldi walked just 4.4 percent of his opponents. In 2019, that rate jumped all the way up to 11.6 percent. Then, in 2020, that fell way back down to 3.5 percent. Again, there are sample size issues in 2020 as he threw only 48 13 innings, but even if you think the number comes up a bit there’s clearly a whole lot of breathing room between 2020 and 2019. And in fact, he’s been in the top five percent of pitchers in walk rate in two of the last three years, but was in the bottom 11 percent in between.

We talk about walk rates with pitchers here fairly regularly, so if you’ve read me before you know the whole spiel about throwing strikes not being the only thing that affects walk rates. Nobody is throwing strikes often enough that chase rate does not come into play as well, and that is the case for Eovaldi as well. In 2018 and 2020, per Baseball Savant, his chase rate came in a bit better than average while it sat a bit worse than average in 2019. That is part of the equation, and specifically he is at his best when he is getting righties to chase that cutter that breaks off the plate.

With that being said, with Eovaldi it does actually come down more to simply throwing strikes. Just like with the walk rate numbers above, the zone rate fluctuations over the last three seasons are jarring. Compared to a league-average rate around 48 percent, in 2018 he hit the zone 55 percent of the time. In 2019, that fell down to the league-average 48 percent before jumping back up to nearly 54 percent in 2020. That’s pretty clear. When he’s at his best, he’s throwing strikes at an elite rate.

If we want to nail it down a little bit further, we can look at his third pitch with the curveball. This is something he really only started throwing with more consistency over the last two seasons as he’s faded the slider out of his arsenal. It can be awfully risky to throw curveballs for strikes, but that’s something of a key for Eovaldi. Velocity is the name of the game for the Red Sox righty, so when a hitter is in the box they are typically sitting and waiting for the fastball, which averages about 97 mph, or the cutter, which sits 91-93.

So when Eovaldi drops in that 80 mph curveball, something he’s done roughly 17 percent of the time in each of the last two seasons, that is often catching batters off guard and they are more likely to let it go. Clearly he wants to avoid hanging one in the middle of the zone because that will go a long way in the other direction, but when he can drop it in the bottom of the zone that’s ideal. When he misses, it’s going to be a ball more often than it will be chased for a swinging strike. Below, you can see the difference in where his curveballs were landing in and around the zone in 2019 compared to 2020.

2019; via Baseball Savant
2020; via Baseball Savant

I’ve gone this far without bringing up the elephant in the room, so I suppose I should bring it up at the close. First and foremost Eovaldi needs to stay healthy. We all know that, and in reality that is the biggest key to his season. But I don’t have anything really to say beyond that because, well, he’s not getting hurt on purpose! If he does indeed stay healthy, though, then he is one of, if not the, biggest keys for the Red Sox this season. Boston needs the top of their rotation to step up, and for Eovaldi there has been a clear line between success and walks, and a clear line between walks and strikes.