Player review: Carson Seymour

2025 stats: 16 G (3 GS) 36 IP, 4.75 ERA, 5.93 xERA, 1.39 WHIP, 6.5 K/9, 3.3 BB/9, 2.3 HR/9, -0.6 fWAR

The San Francisco Giants began the year with three of the five most famous Carsons in western history. Number one, of course, is Johnny Carson. Then there’s Mr. Carson from Downton Abbey. After that, it’s the trio of Carsons who lived on the team’s 40-man roster: Carson Whisenhunt, Carson Ragsdale, and Carson Seymour.

But fame is fleeting, and the Giants no longer enjoy this Carson Trifecta, having designated Ragsdale for assignment at the end of July (he’s now playing in Japan); but also, Whisenhunt seems less like rotation depth and more like trade fodder. Meanwhile, Seymour is a major question mark. Is he a starter or a reliever?

Carson Seymour began 2025 not only as part of a quasi-joke in that Carson Trifecta, but also the #21 prospect in the system according to the McCovey Chronicles community. In Brady’s profile, we see the seeds of what wound up being an… uninspiring major league debut this past season:

Seymour […] is a two-pitch pitcher, with a mid-90s fastball and an excellent slider. That pitch combo might not have earned him a lot of whiffs, but it did somewhat suppress damaging contact: of those aforementioned 92 PCL pitchers, his groundball rate of 53.5% was 11th-highest, while his home runs per nine innings rate of 1.34 was 59th.

He continued to handle Triple-A hitters in 2025, but major league hitters had no problem crushing his unremarkable pitches. He allowed 6 home runs across the first 69 batters and 16 innings pitched and the average exit velocity against his pitches on the season was easily in the bottom 30% of the league. He passes the eye test as a prototypical starting pitcher for the modern game with a 6’6” body and a 96+ mph fastball, but he does not possess that high spin slider the Giants have liked to see high velocity paired with when collecting relievers (but more on this in a moment). While it’s true that he managed to get a lot of groundballs (50 GB%), it’s just as true that when he didn’t induce grounders he did not somewhat suppress damaging contact.

Nine months after that #21 ranking, Brady revisited Seymour and had this to say: “He enters the offseason as someone the team will desperately try to make sure isn’t one of their 13 best pitchers.”

Because of those first 16 innings, he did not pass my eye test during the season — but I’m hardly an authority. His Triple-A line this season was remarkably great: 3.86 ERA in 77 IP with 0.8 HR/9 and 10.5 K/9. He did walk an unsustainably high 4.6 per 9, and if what happened at the majors it that in avoiding walks he wound up catching too much of the plate too often, then maybe there’s still some room for him to grow. On the other hand, it’s hard to see a 6’6” righty with a 96 mph fastball remake himself as a corner pitcher. Not that it’s impossible, just highly unlikely. So, let’s get back to the pitcher he is and not the pitcher that I suggest he could be.

That slider, despite a lack of RPM, does get swing and miss. It carried a 39.3 Whiff% overall. Brooks Baseball notes Seymour’s “sinker generates a very high amount of groundballs compared to other pitchers’ sinkers, is blazing fast, generates more whiffs/swing compared to other pitchers’ sinkers, has slight armside run and has some natural sinking action. Their slider has exceptional depth and has short glove-side cut.” So, when it worked, it worked well, and when it didn’t, batters hit .345, and the struggle was more pronounced against left-handed hitters. Against just lefties, his slider had a 37.1 Whiff% but an opponents’ batting average of .467 (sample size: 67 LHB). Having said that, only 3 of the 9 home runs he allowed came against lefties: Jack Suwinski, Jackson Merrill, and Geraldo Perdomo.

So, when you put it like that, there’s a 30,000 foot view of the profile (and season) that reads, “Small sample size. Let’s see what happens with more experience under his belt. Maybe not intriguing, but certainly solid potential.” That’s the optimist’s perspective. On the other hand, if his only effective pitch against lefties is a sinker (.219 BAA), despite five other pitches, then that’s a problem to me, and if it feels like this review has gone around in circles, it’s because I’m trying in real time to convince myself of what the Giants and others might already see in the player, either because of his overall season or in spite of it.

Seymour got off to such a rough start in the majors that it’s unclear what his role could be in 2026 or even what the organization’s expectations ought to be. Strikeouts, home runs, and walks are what it’s all about and Seymour basically limited walks while running up massive deficits in the other two areas. As a starter, he had one good game against the Cardinals (2 hits, 1 run in 5 IP) and as a reliever he was good mainly in the 1-2 inning role. So, on that 16-game sample alone, that looks like a ROOGY-type bullpen arm to me with a lot of work to do if the intention to use him as a starter remains. His gyro-like slider represents “a different look” that to me works better coming out in short relief as a contrast to the 95+ mph sinker & 2,500+ rpm guys the Giants tend to feature than across multiple innings against a major league lineup.

But on the other hand, perhaps the new coaching staff and coaching plan can refine his cutter or splitter or install a different, more effective pitch mix. In any case, he proved he has some things to work on and the Giants still don’t quite know what they have in Carson Seymour.