How David Peterson Can Improve in 2026

How a refined pitch mix could transform the Mets' All-Star into a more consistent and reliable arm

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David Peterson's 2025 season told two wildly different stories. The left-hander earned his first All-Star selection after a dominant first half, posting a 3.06 ERA and 3.42 FIP through 18 starts. What followed was a massive struggle. Over his final 12 starts, Peterson's ERA drastically increased to 6.34, culminating in a brutal September where he posted a 9.72 ERA over 16.2 innings. With the Mets' busy offseason repairing the team for 2026 and beyond, now is the perfect time to examine what went right, what went wrong, and most importantly, what Peterson can do to bring back his early-season form throughout the entirety of 2026.

What Made Him Successful in 2024

Peterson's initial breakout came in 2024. After returning from hip labrum surgery in late May, he was brilliant, finishing with a career-best 2.90 ERA and a 3.67 FIP across 121 innings while posting a 10-3 record. The key to his success was his heavy reliance on his sinker. Peterson increased his sinker usage to 31.3%, making it his most-used pitch for the first time in his career as seen below. Consequently, he reduced his four-seam fastball to 26.2%, a significant shift from previous years when he relied on the four-seamer as his primary pitch.

This adjustment worked perfectly with his elite extension. He got 7.0 feet of extension, placing him in the 95th percentile for 2024 and contributing to his groundball-inducing ability. His ability to keep the ball on the ground helped him finish with a 50.1% groundball rate and give up just 0.6 HR/9. The sinker-dominant approach gave him an identity and allowed him to attack hitters with a clear plan. His late-season surge was especially notable, posting a 2.41 ERA and an elite 2.77 FIP over his final 67.1 innings while helping the Mets reach the NLCS.

Starting 2025 Strong

Peterson carried that momentum into 2025, looking every bit the reliable arm the Mets had envisioned. Through the first half, he posted a 3.06 ERA and 3.42 FIP. He was consistently the team's most dependable starter, finishing 6 innings in 16 out of his first 24 starts. His pitch arsenal remained balanced with the sinker used at 29.6%, followed by the four-seam fastball at 22.3%, slider at 19.1%, changeup at 15.3%, and curveball at 13.7%.

The sinker continued to grade out excellently, with a +6 Run Value according to Statcast. His curveball and changeup were also highly effective, producing a +5 and +2 Run Value respectively. His slider was less effective with a 0 Run Value. Peterson's season-long 55.4% groundball rate placed him seventh in all of baseball, and his first-half success was predicated on keeping the ball on the ground and limiting hard contact, which he did at a 55.9% rate. His best months came in May, where he produced a 2.30 ERA, and July, where he posted a 1.05 ERA and 3.29 FIP. At 6-foot-6 with elite extension, Peterson made his stuff play up despite below-average velocity, just 14th percentile, and for the first half, it worked brilliantly.

Second Half Collapse

The collapse was quick and rough. Starting in August, Peterson's ERA jumped to 6.68 for the month, then to an astonishing 9.72 in September. The numbers tell a clear story: Peterson's ground ball rate dropped almost 5% to 50% in September, and his FIP drastically increased to 4.46. More concerning, his walk rate increased significantly to 3.78 BB/9, and he struggled to maintain command of all five pitches. This is where his complex arsenal became a liability.

Peterson's four-seam fastball was extremely inefficient, producing a career-worst -7 Run Value over the course of the season. The fatigue factor cannot be ignored. Peterson had never thrown more than 121 innings in any season before 2025, and he reached 152 innings by the end of August. In September, he was throwing more than ever before, and the five-pitch mix that worked early in the year became increasingly difficult to command as his stamina waned. He completely lost control of his four-seamer. What had a 108 Location+ grade in the first half only had a 95 Location+ grade in the second half according to Fangraphs. He also became far less effective in the second half as his four-seam, curveball, and changeup graded out to an 82, 86, and 85 respectively on Fangraphs' Stuff+ model. His strikeout rate actually improved slightly in the second half (8.02 K/9 to 8.6 K/9), but it didn't matter when he couldn't locate consistently nor keep the ball on the ground efficiently.

How To Fix It Going Into 2026

The solution for Peterson heading into 2026 is simplification and commitment to his strengths. First, he needs to significantly reduce or nearly abandon his four-seam fastball, which has been by far his worst pitch by run value. The four-seamer grades out poorly as the 82 Stuff+ second-half grade in 2025 actually represented an upgrade from the 78 Stuff+ first-half grade it received. It's poor in shape, location, and effectiveness, and doesn't fit his groundball-inducing profile. Of the five pitches he throws, it generated the lowest groundball percentage in every year since 2022 and also had the highest xwOBA against in 2025 despite being his second most-thrown pitch.

Instead, Peterson should lean even more heavily on his sinker and changeup. Overall in 2025, those two pitches generated by far the most ground balls for him, with the changeup hit on the ground 65.4% of the time and the sinker a close second at 64.5%. The slider was a distant third at 55.3%, and drastically far behind were the curveball and four-seam at 39.7% and 39.1%. The changeup and sinker each produced an xSLG of .342 and .385 compared to his fastball, which had a much higher .530 xSLG. It is clear that his best pitches are the sinker and changeup.

Something interesting to note is the extremely limited use of the changeup versus lefties. He threw the changeup just 3% of the time against lefties, which is likely a result of his location intentions against lefties. Seen below is the percent of pitches thrown in each location against both lefties and righties, with a clear emphasis on staying down and away against lefties and a more balanced approach against righties. His changeup, as seen below, was largely located down and in (or down and away to a righty), which plays right into a majority of lefties’ strengths, explaining the limited usage.

Pitch Location vs Lefties

Pitch Location vs Righties

Changeup Location vs All Hitters

He was essentially a two-pitch pitcher to lefties, with the sinker and slider combining for 77%. He actually had much success with this approach. Against all lefties he had a .249 xwOBA against compared to a .352 xwOBA against righties. Broken down even further, it was the four-seam that righties hit the hardest with a .407 xwOBA against, and that was his second most-thrown pitch to righties at 25% behind the slider at 26%. His best pitch against righties was the changeup at .309 xwOBA against.

If he can essentially be a two-pitch pitcher versus lefties effectively, he should be able to do something very similar with righties using the sinker and changeup. This would allow him to heavily utilize the sinker-changeup combination well versus righties and the sinker-slider combination versus lefties. The curveball could be used on occasion around the same current 14%, but by drastically increasing changeup usage from 15% to near the sinker usage at 25-30%, it would effectively eliminate the fastball as much as possible and keep it under 10%, only used in extreme circumstances as needed.

The reason the changeup and sinker would play so well off of each other is because of their movement profile. They have nearly identical movement profiles but are separated by about 7 mph. The sinker Peterson throws averaged 7.8 inches of induced vertical break and 14.6 inches of armside run at 91.3 mph in 2025. The changeup averaged 4.6 inches of induced vertical break and the exact same 14.6 inches of armside run thrown at 84.5 mph. This is the exact idea of tunneling that makes it challenging for hitters as it messes with their timing when executed properly.

With an elite sinker, a solid slider, and an underutilized changeup, Peterson would be better served focusing on three primary pitches rather than five. The curveball could still be used as an occasional wrinkle but not as a primary pitch. By differentiating approaches between lefties and righties, it simplifies his game plan as well. This simplification would be especially valuable late in games when fatigue sets in. A sinker-slider-changeup combination gives him everything he needs: a groundball-inducing fastball, a swing-and-miss breaking ball, and an effective changeup that works well off the sinker. The four-seamer is just cluttering his arsenal and creating unnecessary decision fatigue, complexity, and most importantly inefficiency.

Finally, workload management cannot be ignored. At 30 years old entering 2026 and with a history of breaking down late in the season, the Mets should consider occasionally skipping his turn in a six-man rotation to keep him fresh for September. His career-high 168.2 innings in 2025 proved to be too much, and managing his workload more carefully could prevent a late-season collapses.

What This Means For His Contract Situation 

Peterson has one year of arbitration eligibility remaining before hitting free agency after the 2026 season. He's projected to earn around $9.2 million per Spotrac. With playing potential greater than his dollar value for 2026, he is the perfect high-upside arm for the Mets' middle of the rotation, or possibly a very affordable piece for a potential trade partner. Peterson is the perfect pitcher for the Mets and their revamped defense given his heavy reliance on his groundball ability. Peterson represents a solid mid-rotation arm with high upside if he can implement the arsenal changes suggested above and stay consistent throughout a full season. His sinker-first approach and groundball-generating ability make him particularly valuable for teams with strong infield defense, as the Mets seemingly now have with the addition of Semien at second and the addition and transition of Polanco to first.

For the Mets, trading Peterson only makes sense if they can fill another pressing need while maintaining rotation depth. With Kodai Senga's health always uncertain, Sean Manaea in need of a bounceback year, and the trio of McLean, Tong, and Sproat still developing, moving Peterson creates another hole that needs to be filled. It would provide way too much uncertainty unless immediately filled. However, if the right deal emerges for an elite outfielder, relief help, or even another starter, Peterson's value as a proven mid-rotation starter with a high ceiling and being cost-effective makes him a solid piece to any potential suitor. However, at this current moment, unless something pressing comes up, it seems like it would create more questions than answers.

Conclusion

David Peterson showed in the first half of 2025 what he's capable of when healthy and executing his gameplan. The challenge heading into 2026 is sustaining that success over a full season and remaining consistent. By simplifying his arsenal to focus on his sinker, slider, and changeup while abandoning or severely limiting his four-seam fastball, Peterson can become the consistent mid-rotation arm the Mets need, or potentially though less likely, the valuable trade chip that brings back a significant return. His ability to generate ground balls at a high rate combined with his elite extension give him a clear path forward. Whether that path leads to a bounceback year in Queens or a fresh start elsewhere, the blueprint for success is clear: keep it simple, trust the sinker, and use the changeup.