A healthy David Peterson looks to cement himself in the Mets rotation

The narrative around the Mets coming out of spring training was that they simply didn’t have enough pitching. They landed Juan Soto and re-signed Pete Alonso to round out a dynamic lineup, but they lacked a true ace starting pitcher. Then Sean Manaea and Frankie Montas were lost due to injury, converted reliever Clay Holmes was named the Opening Day starter, and baseball fans were quick to pile on.

Yet, heading into Monday’s series-opening game against the Twins, the Mets rank first in baseball with a 2.30 team ERA. Their rotation also ranks first with a 2.55 ERA, and their bullpen is third with a 1.95 ERA. While pitching coach Jeremy Hefner is getting plenty of well-deserved praise, and a lot of words have been written about the early-season success of Tylor Megill, perhaps the most underappreciated member of this rotation has been David Peterson.

The lone left-hander in the starting rotation, Peterson has been with the Mets since being drafted with the 20th overall pick in the 2017 MLB Draft out of the University of Oregon. He was solid enough in his first three years in the minors, but it surprised many when Peterson skipped Triple-A and made his MLB debut during the COVID-shortened 2020 season.

Those 49.2 innings in 2020 started the clock on what has been a fragmented five-year MLB career for Peterson.

He spent time on the IL with shoulder fatigue in 2020 and then was limited to just 66.2 innings in 2021 due to an oblique injury. He split the 2022 season between Triple-A and the majors and then pitched 111 innings in 2023, but also spent part of that season in the minors and was moved to the bullpen for six appearances. Following the 2023 season, he had surgery to repair a damaged labrum in his left hip, which kept him out until almost June last season.

When he returned, Peterson was lights out, pitching to a 2.90 ERA, 1.29 WHIP, and 101:46 K:BB ratio in 121 innings. It was the first time since 2019 that he had made every appearance as a starting pitcher and had also not been demoted to the minors during the season. While many factors contributed to the success Peterson had last season, health may have been the biggest.

“A lot of it started with the hip surgery and getting that cleaned up and just being able to be more efficient with my lower half,” said Peterson earlier this season. “Obviously, being pain-free is nice, but I think being able to be more repeatable with my delivery, knowing that my body is consistently going to give me more than I had, was big.”

Pitching without pain and with repeatable mechanics also led to a small velocity bump for Peterson in 2024, as well as a 5% improvement in his zone rate and a nearly 3% jump in strike rate. His pitches graded out better on pitch models, his location improved, and the quality of contact against him weakened. Not to mention, the improvement he felt mentally from knowing what his role was going to be day in and day out.

“In the previous years, we never really talked about me being in the bullpen until I actually made the move,” recalls Peterson. “Last year, being able to just know what my role was and being able to come back and jump in the rotation and add to the productivity that Sean [Manaea] and Sevy [Luis Severino], and everybody gave us was important. It was important for me to get back and be able to show that I can continue to build on being part of this rotation.”

That consistent role, and the confidence it gave Peterson, allowed him to find a consistency with his performance that he hadn’t been able to lock into in previous seasons. “I had seen what I did last year in stretches and spurts before in my career, but I feel like last year I was able to put it together more consistently,” he explained. “I felt like, this year, going into this off-season being able to get a full off-season of just training and not rehab was big.”

A fully healthy off-season for a starting pitcher means the freedom to tinker and work on your pitches. In previous seasons, Peterson had spent so much time trying to get back to 100% health that he had little time to worry about playing around with grips or modifying pitch shapes. This off-season, he not only had the confidence that he was coming into the season as a member of the starting rotation, but he had the time to work with the Mets coaching staff to tweak some of his arsenal to try and build on his career-best year.

“We’ve been trying to get back to the slider that I had in 2022 and get more of that swing and miss,” explained Peterson. During the 2024 season, Peterson posted solid ratios but had just a 19.8% strikeout rate and a 10.9% swinging strike rate. Both of which were below league average. For comparison’s sake, in 2022, he had a 27.8% strikeout rate and 12.8% swinging strike rate in 105.2 innings with the Mets.

So far in 2025, the swinging strike rate is up on Peterson’s slider, as is the overall strike rate, but the pitch has seen its biggest gains against right-handed hitters. Not only is the swinging strike rate up to righties, but the Ideal Contact Rate (a Pitcher List stat which measures barrels and solid contact and hard groundballs) is down from 57% last year to 25% this year. That’s huge for Peterson since the only other pitch he throws to righties that had at least an average swinging strike last year is his four-seam fastball.

“I think the back foot [slider to righties], for me, is a good miss,” explained Peterson, “but I think for us more overall, it’s just kind of being down with the slider, being over the plate, making it look like a strong a strike as long as possible is the goal.”

So far, through three starts, Peterson is executing exactly as he and the team wanted. The zone rate on his slider is down almost 7%, which means it lands in the strike zone less often; however, the chase rate is up, and the pitch is thriving as a two-strike offering. In 2024, the PutAway Rate on Peterson’s slider, which measures how often a two-strike pitch results in a strikeout, was 19.2%. The MLB average was 19.1%. So far in 2025, his PutAway Rate on the slider is a ridiculous 36%.

While some of that might be tightening up the movement of the pitch, the biggest component, as Peterson alluded to, is the location. The left-hander has thrown the slider in the lower third of the strike zone (or below) 87% of the time this season, up from 74% last year. The pitch is starting as a strike and then falling out of the strike zone, hence the lower zone rate, but getting more swings and misses. Exactly the change the 29-year-old wanted.

Yet, it’s not the only change that Peterson was looking to make in the off-season.

“We put some emphasis on continuing to improve my four-seam in terms of the vert [vertical movement] and create the separation with the sinker,” he said. “Being primarily a sinker guy growing up and in college, I use the four-seam a lot out of the zone for chase up.”

The location of Peterson’s four-seam fastball is crucial for its success because he only throws 93 mph. However, he gets elite 7.1 feet of extension on his release, so the ball is released closer to home plate than average, which can make it look faster. Like a lot of left-handers, Peterson’s fastball has some natural horizontal run, so it’s not a typical flat fastball that thrives up in the zone, but through three starts this season, Peterson has added over one inch of Induced Vertical Break (iVB) on his four-seam, which has given it a flatter approach angle. That means it fights against gravity a bit more as it approaches home plate and seems to “rise” a bit more than it had previously. A fastball like that tends to thrive more up in the zone, which is what Peterson wants.

However, in execution, the pitch has been lacking a bit to start the season. He is throwing it in the strike zone more often, but he’s not getting it up in the zone as much as he wants, leaving it in the middle of the zone too often, which has led to a drop in swinging strike rate and an increase in hard contact rate allowed. The same is happening with Peterson’s changeup and is a big reason why his strikeout rate is up, but his overall swinging strike rate is down 4%.

“I think there’s gonna be a little give and take,” Peterson admitted about his four-seam approach, “but I think a lot of it is probably small sample size [right now], but being able to use the four seam up in the zone and giving the hitters two different fastballs looks has been big [for me].”

It also provides another opportunity for growth as the season goes on. Peterson’s new approach with his slider is working just as planned, and the shape of the fastball appears to be on target as well. If he can continue to improve his fastball and changeup locations, then we could see the left-hander miss even more bats and start to chip away at that elevated .317 BABIP.

With a start this week against a Cardinals team that ranks 3rd in baseball with a .784 OPS, Peterson will have perhaps the toughest test of his new pitching philosophy. If he can survive that, and continue to execute on the changes the Mets have laid out for him, his breakout 2024 season may wind up just being the precursor to an even better 2025.