What’s behind Nick Pivetta’s recent turnaround?

The Red Sox are looking to come back from an absolutely hideous loss on Tuesday in which Nathan Eovaldi tied a major-league record allowing five home runs in a single inning, and they turn to Nick Pivetta to try and salvage this series and still take two of three from the Astros. Pivetta has been one of the stories of this rough start to the season, coming in as the team’s de facto number two starter and looking to take a leap from what was already an impressive 2021 relative to expectations but ultimately scuffling mightily in the first month of the season. His overall numbers for 2022 still don’t look very good, but there is some reason for confidence tonight as Pivetta has certainly looked much improved over his last two or three starts.

Consider that through the month of April, the former Phillie had pitched to an 8.27 ERA through four starts with a FIP of 6.70 that wasn’t much better. His control was all over the place, and when he was hitting the zone it was mostly getting crushed. But in May, things have looked much better with a 2.08 ERA over three starts to go with a 1.47 FIP. Pivetta is always something of a rollercoaster, of course, which is why there were so many believers even after he flamed out in Philadelphia, but this has been an extreme. Still, something is clearly different, but we want to pin down exactly what has changed and if it’s something that we can see continuing, or at least staying in the general ballpark of this performance, moving forward.

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To start with, I think we have to acknowledge that the schedule has been much more favorable for Pivetta in his recent starts compared to April. Over his first four starts he faced the Yankees, the Twins, and then the Blue Jays twice. By wRC+, both the Yankees and Twins have been top 10 offenses this season (with New York holding down the top spot), while Toronto has been more middling but certainly has big names that can beat any pitcher. Meanwhile in May, he has faced the Orioles, White Sox, and Rangers, all of whom are in the bottom third of the league by wRC+. So it would be disingenuous to mention this improvement from the Red Sox righty without mentioning the glaring difference in schedule.

At the same time, there have been other tangible improvements made that should theoretically get his performance back to an equilibrium even against strong opponents. A lot of that has to do with his control and walk rate. Over his first four starts, Pivetta walked a whopping 16.7 percent of his opponents. Since the start of May, he’s walked only two batters for a 1.5 percent rate. Some of that comes down to simply hitting the zone more often, with a four percentage point increase getting his zone rate up to roughly 45 percent in his last three starts, but it’s also getting chases. Below you can see a game-by-game visual representation of how many swings Pivetta has been getting on pitches out of the zone compared to how often he hits the zone. He’s been striking a nice balance between zone rate and chase (O-Swing) rate.

A lot of this is also reflected in the improved quality of his breaking stuff, which is hugely important for him given how little he throws his changeup. If his breaking stuff is getting hit hard, he’s just not going to succeed. Looking at his early starts on Baseball Savant, at least one of his breaking balls — he leans on both a slider and a curveball — was getting hit hard in those outings. More recently, both pitches have performed well in part because he’s getting better break on them and making them appear more enticing to his opponent, leading to more of those aforementioned chases.

And while it’s the breaking balls that are getting better results, to me it looks like a lot of this comes down to the fastball, which serves to set up the other pitches for Pivetta. It’s a very common approach for pitchers in today’s game to keep the fastball up in the zone to set up for attacking down in the zone with offspeed and breaking stuff later in the count. Early in the season, Pivetta was not doing a good job of that, with his fastballs either missing way above the zone in non-competitive spots or, worse, missing in the middle of the zone and getting crushed. More recently, he’s done a better job of peppering the top of the zone and just above it to keep hitters honest in that zone before dropping the breaking ball and getting those swings and misses and weak contact on pitches out of the zone. I won’t waste your RAM posting the zone plots from every game, but as an example below is a comparison of his last start against the Rangers and one of his early starts against the Twins.

Tonight is a big start for Pivetta even taking away the significance for the team trying to win a second straight series. He will be facing an Astros team that looks a lot more like his April competition than May, ranking second in baseball this year in wRC+. One start won’t give a whole answer, of course, but we’ll be closer to knowing if this turnaround has been more about competition or real change. To me, it looks like there is some real change here with his fastball command and everything else that can dovetail off of that. If Pivetta is locating that fastball where he wants and avoiding non-competitive offerings and meatballs over the plate, I think he can hold his own, even if he’s not quite as dominant as his last few outings. If not, it could be another long night, for us as fans and for the bullpen.