David Peterson’s Mixed Results: Why Mets Southpaw Is Struggling

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David Peterson‘s mixed results have been a potentially troubling sign for the New York Mets. Peterson was a bright spot in the Mets’ bleak 2020 season. The lefty posted an impressive 126 ERA+ over 50 innings, essentially serving as the Mets’ SP2 as the rest of the rotation crumbled around ace Jacob deGrom. As the Mets’ new ownership prepared for the 2021 season, they put their faith in Peterson, setting him up as the Mets’ fifth starter — at least until the return of Noah Syndergaard. However, Peterson currently holds a 4.97 ERA in 38.0 IP. In a year where hitting has dropped off league-wide, why is Peterson seeing worse results?

David Peterson’s Mixed Results: Recipe for Success

In 2020, Peterson wasn’t the flashiest pitcher, but he found success by limiting home runs and inducing ground balls and soft contact. He had a pitch mix consisting of about 40% four-seam fastballs, a good slider which he threw for about 25% of pitches, and a changeup that he threw about 20% of the time. In addition to this, he would also mix in a sinker for the remaining 15%. The four-seam/slider combination seemed to be working especially well, as BaseballSavant rates them as having run values of -5 and -6, respectively.

David Peterson’s Mixed Results: A Change in Approach

After his solid rookie campaign, Peterson seems to have made some significant changes to his approach in 2021. The sinker he used only occasionally in 2020 has jumped up to nearly 40%, now being used as his primary pitch. Consequently, the four-seam fastball has dropped below 25% usage.

While the sample size is not particularly large, this change in approach has seen a leveling out in the effectiveness of his entire repertoire. Currently, they all sit between 0 and +3 in terms of run value. Potentially, the switch from four-seam to sinker usage has inhibited Peterson’s ability to set up his slider, which was his best pitch in 2020.

So, why the sudden change in approach? This may be part of an overall trend in the Mets pitching staff, as similar albeit less drastic changes have been seen in pitchers Marcus Stroman, Taijuan Walker, and Robert Gsellman. Thus far, it seems to be working well for guys like Gsellman, who is now successfully generating soft ground balls rather than giving up hard hits while trying to go for strikeouts.

David Peterson’s Mixed Results: Looking Forward

While it does seem like Peterson has made a purposeful change in his pitch usage, a larger sample may be needed to see if it will yield positive results. Confoundingly, despite a higher ERA this year, Peterson has decreased his BB/9 by 1.0, while increasing his K/9 by more than 3.0. On top of this, in a year where hitting is down leaguewide (likely due to altering the baseball), Peterson has managed to give up more hits and more home runs.

Peterson’s 2021 stats may also be inflated by his tendency to have blow-up innings. In his first start of the year, he gave up six runs to the Phillies in just four innings. Then on May 7 against the Diamondbacks, he was off to a good start before allowing four straight batters to reach via walk or HBP, including the opposing pitcher. This led to three runs and Peterson being pulled from the game in just the second inning.

David Peterson’s 2021 season has been concerning at times, but he has shown a number of positive signs as well. Especially now that the Mets still have four starting pitchers and an entire lineup on the IL, they’ll look to Peterson to give them a chance at a W every fifth day.

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David Murtha is an MLB writer covering the New York Mets as well as general baseball news. He is a lifelong Mets fan born and raised in Queens. He is also currently a student at Stony Brook University studying biology, and has previously written for other online publications.