Mariners Primer: Bullpen
Can Seattle's relievers preserve the good work of the rotation on a consistent basis?
Seattle relievers weren’t in the same class as the starting staff in 2024. But with the exception of home runs and walks, the unit’s numbers were better-than-average or top-shelf in some instances.
Still, the bullpen was challenged to keep pace as the season progressed. Losing a pair of crucial late-inning relievers, Matt Brash and Gregory Santos, in Spring Training was a severe setback before the season even began.
Brash missed the entire year recovering from Tommy John surgery. Meanwhile, Santos appeared in just eight games due to a lat strain and then biceps inflammation.
Notable departures: JT Chargois, Austin Voth, Yimi GarcÃa
Looking ahead
The Mariners didn’t make a major addition to the bullpen this offseason, as they did by trading for Santos in February 2024. Instead, with the exception of a few low-profile newcomers, the team will heavily rely on holdovers from last year.
Andrés Muñoz remains in the closer role. Muñoz held opponents to a .153 AVG, which was fourth-lowest among relievers facing 200-plus batters. His .267 xwOBA was much better than the MLB average for relievers (.307), although it was only good enough to rank 26th.
Expected Weighted On-Base Average (xwOBA) uses quality of contact (exit velocity and launch angle) to determine what should’ve happened to batted balls. A key advantage to xwOBA is defense (good or bad) doesn’t influence it. This gives us a truer sense of how a hitter or pitcher is performing.
Barring unforeseen circumstances, Santos will be in the Opening Day bullpen. Obviously, the Mariners want to see the pitcher who appeared in 60 games and had a .276 xwOBA with the White Sox in 2023. Still, taking a wait-and-see approach with the hard-throwing right-hander makes sense. Particularly, early in the season.
Santos set a career-high for innings in a big way during his final campaign in Chicago. Expecting him to approach 60 frames in 2025 may be a big ask considering his injury challenges last year and the fact that he was shut down in September 2023 due to elbow inflammation.
Gregory Santos’ Workload as a Professional
2016 - 41 innings
2017 - 48 innings
2018 - 49 innings
2019 - 34.2 innings
2020 - Did not pitch (pandemic)
2021 - 30.2 innings
2022 - 38.2 innings
2023 - 66.1 innings
2024 - 14.2 innings
Santos has been pitching in Cactus League games every 3-4 days. Perhaps he’s making additional appearances in competitive situations not captured by his MLB page. That said, I suspect the team errs on the side of caution with the 25-year-old and judiciously ramps up his workload.
Collin Snider enjoyed a breakout campaign in 2024 highlighted by personal bests in strikeout and walk rates, xwOBA, and ERA. That said, Snider’s .308 xwOBA was league-average due to a 10.1-percent barrel rate that ranked in the bottom 10-percent of 230 relievers.
Last year, Trent Thornton (71 appearances) was the most frequently used Seattle reliever. Thornton’s overall results were a step back compared to 2023. The former North Carolina Tar Heel struck out hitters more often. But he experienced a spike in loud contact.
Still, Thornton was superb last September when he held opponents to a .103 SLG, which was eight-best among pitchers facing 30-plus hitters.
After a great debut with the Mariners in 2023, Gabe Speier missed all of last June and most of July with a rotator cuff strain. When Speier was available, he was less effective than the season prior. The lefty did strike out a career-high 31.7-percent of the batters he faced last year. But his walk rate rose eight points to 13.5-percent. Also, the California native’s four-seam fastball velocity was down about 2-mph from his first campaign with Seattle.
Opponents produced a .240 AVG against left-hander Tayler Saucedo, which was higher than the standard for relievers last year (.234). Still, Saucedo managed to minimize hard contact. Among 232 relievers, the Tahoma High School product’s 27.8-percent hard-hit rate was fourth best. The only southpaw ahead of Saucedo was Tanner Scott (27.5-percent).
A reliever on this nerd’s radar is Eduard Bazardo. The right-hander’s .243 xwOBA and 4.5-percent barrel rate were best among Seattle pitchers facing 100 hitters. Furthermore, Muñoz was the lone Mariner with a lower SLG than the Venezuelan. Granted, Bazardo wasn’t a high-leverage arm last year. But his numbers are intriguing.
Reliever pool (2024 xwOBA)
Andrés Muñoz (.267)
Collin Snider (.308)
Gregory Santos (.270)
Trent Thornton (.284)
Tayler Saucedo (.275)
Gabe Speier (.279)
Carlos Vargas (MiLB)
Eduard Bazardo (.243)
Cody Bolton (.306)
Hagen Danner (MiLB)
Will Klein (MiLB)
Casey Legumina (.336)
Josh Fleming (.320) +
Austin Kitchen (MiLB) +
Peyton Alford (MiLB) +
Adonis Medina (MiLB) +
Sauryn Lao (MiLB) +
Shintaro Fujinami (MiLB) +
Matt Brash (DNP)*+
Troy Taylor (.278)*
Jackson Kowar ( DNP)*+
Trevor Gott ( DNP)*+
* Injured
+ Not on 40-man roster
Several noteworthy relievers who could potentially make an impact this season won’t be with the club on Opening Day. The first is Brash. The Canadian made his first appearance in the last game of Spring Training. Officially, he projects to be back in about a month. But it’s important to remember any pitcher recovering from a serious arm injury is susceptible to setbacks.
Two seasons ago, Brash led MLB with 78 appearances and had a ninth-best 34.7-percent strikeout rate. Still, we should remember that the 26-year-old has a history of control issues. He had a worse-than-average 9.4-percent walk rate in 2023, which was over five percent better than his rookie campaign. Also, opponents had a .242 AVG and .325 OBP against the right-hander, which were average-ish.
As with Santos, it’s reasonable to expect the Mariners will be cautious with Brash’s workload once he returns to the big-league club.
Casey Legumina has been receiving favorable comparisons to former Mariners closer Paul Sewald. But the Gonzaga product will start the season in the minor leagues. Then again, Sewald started the 2021 season with Class-AAA Tacoma before joining the big-league club in May and quickly becoming a formidable late-inning weapon.
Troy Taylor, who is currently dealing with a lat strain, made his MLB debut last August. Taylor struck out an impressive 30.9-percent of the 81 hitters he faced. But the 23-year-old was burned by damaging contact. While he held hitters to a .207 AVG, eight of 15 hits allowed were of the extra-base variety.
Former Mariner Trevor Gott is rehabbing from Tommy John surgery he underwent about a year ago. If all goes well, the 32-year-old could join the team by midseason.
Japanese hurler Shintaro Fujinami spent last year in the Mets organization. A shoulder injury cost him a large portion of the season. When Fujinami returned, he was assigned to Class-AAA Syracuse due to ineffectiveness. The right-hander had an impressive 27.5-percent strikeout rate in 33 appearances. However, his 22.3-percent walk rate was sixth-highest among 516 AAA pitchers.
Outlook
As relievers go, Muñoz is the surest thing the Mariners have. But after that, the situation becomes a bit murky in my eyes. Which arms will be the best options to serve as a bridge between the starting staff and the closer?
Seattle has an interesting stable of relievers. But the team is banking on rebounds by pitchers without multiple years of MLB success on their résumé. Perhaps Speier and Thornton enjoy bounce back campaigns. Maybe Santos and Brash are, once again, late-inning fixtures by the summer. That’s a lot of hope heading into the season.
Then again, helping pitchers become the best version of themselves is a core competency of the Mariners organization. Recent success stories include Justin Topa, Isaiah Campbell, Penn Murfee, Erik Swanson, Sewald, Thornton, Speier, and Saucedo. It’s plausible Snider, Bazardo, and Taylor will be the next wave of diamonds in the rough that become key bullpen pieces.
Still, I would feel a lot better about the Mariners if I knew for certain that Santos and Brash would be good to go this year. Since I don’t, I remain guarded about the bullpen’s outlook with Opening Day upon us.
My Oh My…
