David Peterson optimizes his sinker

I’ve been wanting to write about David Peterson for a while now. Virtually out of nowhere, Peterson emerged as a rotation cog and postseason hero for the inspiring Mets. Despite not debuting until Memorial Day, he accumulated a career-high 1.9 fWAR while pitching to a career-best 2.90 ERA and 3.67 FIP. 

But here’s the thing: The underlying metrics aren’t buying it. Peterson’s Savant page is full of those dreaded blue circles; his xFIP — 4.10 — was higher than each of the last three seasons; he generated whiffs at a career-worst rate that sat below league-average. 

The contrast intrigued me. This is a 29-year-old pitcher who revitalized his career in the wake of extensive hip surgery with an undeniably strong, consistent season. How did he do it, and can he replicate his success moving forward? 

Peterson’s story begins with his sinker. Major League Baseball witnessed a modest sinker renaissance in 2024. All together, the league threw 16% sinkers this year, the highest single-season percentage since 2019. Clumped together, the sinkers were effective: They allowed a .342 wOBA (the second-lowest mark in the last decade) and a Pitcher Run Value of 30 which, while below last year’s PRV of 121, is only the second time in the Pitch Tracking Era that sinkers have accrued a positive PRV. 

There are a number of reasons for this, whether that’s increased sinker velocity or the extinction of abortive sinkers in favor of other, more successful pitches. But what is most pertinent to Peterson is the concept of sinker optimization, which Justin Choi first wrote about in 2023. Much in the vein of a splitter serving as a platoon-friendly pitch and a slider posing as platoon-adverse, sinkers aren’t platoon-neutral. Instead, they fare better against same-side hitters. Viewing the pitch through a two-year window, Peterson seemed to take this to heart:

Peterson’s Sinker Usage	2022	2024
vs. LHB	12.3%	42.3%
vs. RHB	11.3%	27.2%

Peterson’s Sinker (x)wOBA	2022	2024
vs. LHB	.115 wOBA, .233 xWOBA	.220 wOBA, .260 xWOBA
vs. RHB	.422 wOBA, .397 xWOBA	.356 wOBA, .402 xWOBA

The increase in sinker usage didn’t come as an even split. Peterson’s sinker is his undisputed No. 1 offering against left-handed hitters, and it’s been an effective pitch for a while now. He even increased his same-side sinker usage as the year went along, peaking at a 46% usage rate against LHB in August. Conversely, he decreased his opposite-side sinker usage, with a nadir of 22.8% in September. And that makes sense, because his sinker is markedly less productive against righties, as a platoon-based pitch. Moving forward, he ought to consider widening that discrepancy even further. 

This all fits into the greater narrative of Peterson’s sinker, as he explained to reporters in August:

“I’m just trying to find a good balance of where to use the sinker or where to use the four-seamer and then let the numbers shake out how they do as the game goes along.” 

As a two-fastball pitcher, deploying those pitches then becomes a task of optimization. And beyond embracing his sinker as a platoon-based pitch, Peterson developed a niche for his sinker as a strike-throwing weapon to use in situations that troubled him in the past. 

Peterson excelled this year in part because he lived in the strike zone, with a career-best Zone% (48.5%) and a career-best 1st Pitch Strike% (63.5%). Among SPs with at least 20 GS, Peterson threw the sixth-most pitches in the zone, while he saw the third-largest increase in first pitch strikes among qualified starting pitchers. In total, he slashed his BB/9 to a career-low 3.42. 

Look at how this affected Peterson in the situation that pitchers face the most, 0-0 counts: 

• League: .384 wOBA

• Peterson in 2023: .543 wOBA

• Peterson in 2024: .279 wOBA

Why the difference? It starts with his sinker: 

Peterson’s Fastball Usage on 0-0 Counts	2023	2024
4-Seam Fastball	27.7%	19.7%
Sinker	32%	41%

And if we look exclusively at the strike-throwing capabilities of his preferred option to start an at-bat in each of the last two seasons: 

Peterson’s No. 1 option on 0-0 counts	Balls	Called Strikes
2023 4-Seam Fastball	51.8% (71)	22.6% (31)
2024 Sinker	28.2% (59)	36.1% (76)

That’s pretty damning. The pitch (4-seam fastball) that Peterson used most frequently to begin an at-bat in 2023 was a ball over half the time. Right away, he was at a disadvantage. 

Of the plate appearances that didn’t end in one pitch, Peterson is getting to an 0-1 count more often (57%) in 2024 than he did 2023 (52%). Plus, beyond improving his odds at an 0-1 count, the sinker helped Peterson limit the damage on 0-0 counts, holding the opposition to a .197 wOBA — compared to the .553 wOBA allowed on 0-0 counts by his 4-seam fastball in 2023. 

The second situation that Peterson’s sinker remedied comes when he falls behind in the count. In the past, Peterson relied on his 4-seamer in these situations. But, first in 2023 and then even more so in 2024, Peterson turned to his sinker. While the results weren’t always positive, the expected stats agree with the decision-making. 

Peterson’s Fastball Behind in the Count	wOBA	xWOBA
4-Seam Fastball	.347	.472
Sinker	.374	.402

The logic behind the decision is sound, too: Due to its tendency to induce ground balls, a sinker is less likely to be barreled than a 4-seam fastball (5% vs. 6.6%). That certainly held true for Peterson, who ranked in the 59th percentile in Barrel% despite sitting in just the 16th percentile in Hard Hit%.

It’s also worth viewing Peterson’s sinker within the context of the Mets, who embraced this counterrevolution more so than any staff in the majors. New York had four starting pitchers — Sean Manaea, Luis Severino, Jose Quintana and Peterson — throw a sinker more than 25% of the time. Only the Phillies had more than two starting pitchers fit that description. 

“It’s just a natural cycle of the game because of the way the hitters are trying to get on top of the heater now,” pitching coach Jeremy Hefner told The Athletic in May. 

Hefner mentioned that the Mets now have a better understanding of what makes a good sinker, noting that the pitch must possess either depth or run — with the exact characteristics contingent on the individual pitcher. FanGraphs likes the shape of Peterson’s sinker (102 Stuff+), and it’s vastly superior to his 4-seam fastball (70 Stuff+). When it comes to sinkers specifically, Peterson’s ranks favorably: 13th-highest among SP with 100 IP, and the highest among any SP on the Mets. 

That’s because Peterson’s sinker has a lot of depth, ranking in the upper quartile among sinkers when it comes to vertical drop — in fact, since 2021, he’s added nearly six inches of drop to his sinker. On the flipside, in that span he’s also lost nearly an inch of arm side movement. In the process, he’s developed a weapon. His sinker had a negative RV/100 in each of his first three years in the league, and has produced a positive RV/100 in each of his last two seasons. That’s a testament to the Mets, and their ability to craft Peterson’s sinker into a pitch that satisfies one of the two buckets for successful sinkers. 

For Peterson, it all boils down to optimization. In optimizing the sinker’s shape, Peterson created a pitch that best addresses his weaknesses. And in recognizing the sinker’s status as a platoon-based pitch, Peterson maximized the effectiveness of his new pitch, too. Now, he has a blueprint for further success, with an uptick in usage against left-handed batters and added depth helping him limit barrels and throw strikes.