40 in 40 2025: Gregory Santos

Gregory Santos is ready to hit reset and slide into the 2025 bullpen

The Seattle Mariners bullpen is known for the many successes plucked out of the pile, but in order to find the diamonds in the rough, you need to go through the rough first. It remains to be seen if Gregory Santos can be one of those sought after diamonds, another jeweled feather in the M’s bullpen cap, but there was a time where we dreamed on that potential. As long ago as last offseason. The Mariners acquired Santos on February 3rd of 2024, and it culminated at the end of an interesting chain of transactions. There was a lot of hope at the time that Santos could perhaps be the third proverbial head in a revived pitching Cerberus, as our own Zach Gottschalk mused in Santos’ 2024 40 in 40. And, the hope was far from unfounded.

Santos is your usual slider-heater combo bullpen arm and going back to his 2023 with the Chicago White Sox, to great effect. That season he posted in 60 different games, and logged 66.1 innings pitched doing so. Using a sinker a little less than half the time, the pitch had a -5 run value overall (-1.0 RV/100), but his slider more than made up for it with a 15 RV (2.7 RV/100). With a 17% K-BB and a 79 ERA- and 60 FIP- that season, it’s understandable why everyone was very excited about the possibility of Gregory Santos, Mariners bullpen weapon. But in 2024, it wasn’t meant to be.

Immediately at the start of the season Santos was sidelined with injury, dealing with a latissimus dorsi strain. He made a brief appearance around July before returning to being injured for most of the rest of the season, his second trip to the IL because of right biceps inflammation. In total for the M’s in 2024 Santos appeared in 8 different games for 7.1 innings. I could tell you about his K-BB being close to his ‘23 numbers or about how his ERA- was very bad or how his FIP- was very good but also no I won’t because it was 8 games and 7.1 innings.

The projections this year see him going as high as his ‘23 numbers with the White Sox and similar numbers in terms of strikeouts and results, but PECOTA is far less kind, both in amount of work and results and value. If he can stay healthy and reach his potential then the Mariners might truly have a different landscape for their bullpen that even they are yet to achieve, but that is relying on not one but two ifs so caution or needing to see it to believe it are valid approaches.

Projections:

FGDC: 62.0 IP, 1.1 fWAR 2.95/2.98 ERA/FIP
PECOTA: 45.0 IP, -0.1 WARP, 4.75/4.12 ERA/DRA

Overs/Unders:

Connor: Under

I do think Santos will be effective when he’s healthy, but considering we saw him appear in just eight games last year, his 2025 outlook remains unclear. He was more myth than man in 2024, and the only way I see him matching these projections is if he’s able to pitch all season, which given how last year went, could be a tall order.

Kate: Under

Have you ever been the custodian of something beautiful, but finicky? Perhaps it was a classic car, or a particularly slippery bit of beaded vintage fabric, or a very very purebred cat? This is Gregory Santos. So beautiful as an idea, so very rarely in fully operational order. I am taking the under, only because I am agnostic, and struggle mightily with believing in things I cannot see. But I would love to have the full faith to take the over; I just want to see it from the Mariners front office first.

Max: Over

This is purely a vibes pick. Santos is the exact kind of pitcher I love to watch, and I’d prefer to watch him be a good pitcher instead of a bad one. Stay on the mound and let 103 eat, Gregory. This bullpen needs you.