David Peterson Is A Mets Mystery Box

The New York Mets are turning back to David Peterson in their starting rotation, and just like their season, success hinges on razor-thin margins. When everything is clicking for Peterson, he throws enough strikes to limit walks, get ahead in the count, and generate ground balls to keep the game within reach. It isn’t an overwhelming or dominant game plan, but it will get guys out, keep the bullpen from being overtaxed, and get you a start closer to the guys you really trust. 

For the first four months of the 2025 season, Mets fans were treated to the best possible outcome of this profile. Over 21 starts, through August 1, Peterson posted a 2.83 ERA, with the Mets going 12-9 in his starts. Unfortunately, his final nine starts saw his ERA balloon to 8.42, during which the Mets went 3-6 and fell out of the playoff race. But here’s the thing: Peterson didn’t actually pitch all that much worse. His FIP was 3.36 over his first 21 starts, and 3.88 over his final nine. 

The reality is that Peterson’s effectiveness is somewhat left to chance. He doesn’t possess overwhelming stuff, and, paradoxically, he isn’t particularly adept at generating soft contact. What he does do is direct contact towards the ground, which limits damage and allows him to weather a lineup multiple times. Adding more variance into the equation is that Peterson is one of the most difficult players to project. 

This is anecdotal analysis, but few players have a larger divergence between their ERA estimators. For his career, he has a FIP of 3.91, an xERA of 4.65, and a SIERA of 4.14, against a career ERA of 4.16. While that makes SIERA look like the golden goose, when you look at all of this data season over season, the relationship cracks. 

What does this all mean? In effect, prognosticating Peterson’s future performance based on generally reliable ERA estimators isn’t quite so simple. SIERA has done a good job mirroring his career ERA, but xERA, which has the largest difference between his career ERA, has the smallest season-to-season standard deviation. This dynamic is interesting in its own right, but it makes talking about Peterson’s future performance a bit murky. However, we can talk about how Peterson, and his admittedly limited profile, can prosper. 

One of my personal sports analysis idioms is, “the main thing has to be the main thing.” The basic conceit is that every professional athlete has some singular core skill that is the foundation of their game. Remember Matt Harvey? His main thing was that he could throw four-seam fastballs down Main Street and prosper. When he stopped being able to do that, he was out of the league in short order. For David Peterson, the main thing is that he’ll throw his sinker and then hope for the best.

The bread and butter of Peterson’s approach is that he can coax favorable launch angles. At the end of the day, it doesn’t really matter how hard you hit the ball if you hit it on the ground. For a pitcher who doesn’t rack up strikeouts, limit hard contact, or own a microscopic walk rate, it’s basically the only way you can survive in the majors. The problem that Peterson has run into this season is that his sinker has gone from a worm burner to a low-flying hazard. 

Last season, batters tagged Peterson’s sinker for an average exit velocity of 90.4 MPH and an average launch angle of -2 degrees. It led to a wOBA of .350, an xwOBA of .351, and a slugging percentage of .391. All told, the pitch was worth six runs of value or 0.7 runs per 100 pitches. Peterson’s sinker was by no means an elite pitch, but it was a solid enough base to get disadvantaged hitters to chase his off-speed pitches off the plate. 

This season, Peterson’s sinker has become an indescribable liability. Batters are hitting it for an average exit velocity of 95.7 MPH and at an average launch angle of 7 degrees. Unsurprisingly, that’s led to a wOBA of .487, an xwOBA of .517, and a slugging percentage of .594. That may not be the worst individual pitch in the majors, but it’s certainly in the running. So, what exactly caused his sinker to sink into the abyss? 

The first noticeable change is that Peterson is getting far less horizontal movement on the pitch. Last season, he generated 14.6 inches of arm-side movement, but that has decreased to 12.1 inches in 2026. For a sinker that averages 91.3 MPH, that loss of movement might have completely nuked the pitch's viability. On top of the loss of movement, Peterson hasn’t been locating it in nearly as advantageous locations. 

The first image shows Peterson’s sinker locations in 2025, while the second shows 2026. What stands out?

The volume of pitches he has left in the middle-outer third of the plate has exploded, and hitters are absolutely teeing off on it, posting an .846 slugging on balls in play. It’s likely that with the sinker’s slightly diminished movement profile, it’s catching more of the plate and running away from fewer barrels than before. In many respects, it’s the worst of both worlds. 

So, what’s the best path forward for Peterson? I’d suggest throwing fewer sinkers for one. He has always had a junkerballer profile, but has consistently thrown his mediocre-at-best fastballs over 50% of the time. His slider has been a highly effective pitch this season and could keep hitters off his sinker a bit. However, I think the most likely outcome is that either he starts throwing his sinker more effectively by hitting better spots and/or generating more movement, or he finds himself out of the rotation again. The margins are razor-thin, and it’s sink or sinker for David Peterson.