Former Mariners Bullpen Gamble Gets New Life With Giants After Injury-Riddled Stint

Gregory Santos’ return to the Giants is not a major Mariners regret story, at least not yet. It’s more of a reminder of how quickly a sensible bullpen gamble can disappear when injuries take over. Seattle acquired Santos in 2024 hoping his power sinker and late-inning upside would give the bullpen another nasty look. Two injury-filled seasons later, the Mariners never really got enough of him to know what they had.

The Giants are giving Santos another shot after selecting his contract from Triple-A Sacramento. For Mariners fans, that news lands like a tired sigh from a fanbase that remembers exactly what Seattle thought it was getting and exactly how little of it ever actually got.

The Mariners traded for him in February 2024 because his 2023 breakout with the White Sox looked like the blueprint for a nasty high-leverage weapon. Santos had a 3.39 ERA, five saves, a heavy ground-ball profile, strong walk numbers, and the kind of upper-90s sinker that makes bullpen coaches start seeing leverage innings in their sleep.

Gregory Santos’ Giants Return Brings Mariners’ Unfinished Bullpen Bet Back Into View

On paper, it made sense. The Mariners love power arms and controllable relievers. They also love finding the guy before the rest of the league fully buys in. Santos looked like one of those classic Seattle upside plays where the front office bets on the idea that their pitching infrastructure can polish the rest.

The problem is that the Mariners basically never got to evaluate the real version of him. Santos’ Seattle tenure became one long injury receipt. A right lat strain delayed his debut until July 2024. Then biceps inflammation interrupted him again after he had barely gotten settled. He finished that season with just eight appearances, a 4.91 ERA and 7 1/3 innings.

Then came 2025, and things somehow got even messier. Santos appeared in just eight more games, posted a 5.14 ERA over seven innings, walked eight batters and didn’t record a strikeout. That last part still feels fake even when you see it written down. A high-velocity reliever with swing-and-miss upside going seven innings without a punchout is exactly the kind of stat that tells you something was deeply off. Then knee trouble and cartilage cleanup surgery essentially ended any chance of a clean reset.

The Giants aren’t just doing this off memory. Santos has actually pitched well at Triple-A Sacramento, carrying a 2.45 ERA while holding opponents to a .220 batting average. That at least gives San Francisco a baseball reason to see what is left here, even if there has been a little recent wobble with two of his three earned runs allowed coming in his last two outings.

So when Seattle non-tendered him after the 2025 season, it was hard to frame it as an outrageous mistake. The Mariners were moving on from an idea that had never become an actual usable roster piece.

This Giants development could be irritating without being damning for some. If Santos goes to San Francisco and starts throwing darts again, Mariners fans are allowed to be annoyed. Nobody wants to watch another team get the healthy version of a player their own club waited two years to see. It’s like buying a fancy appliance, watching it break immediately, returning it, and then seeing your neighbor post about how great theirs works. Cool, love that for everyone.

The Mariners chased a high-leverage bullpen answer and ended up with 16 appearances, 14 1/3 innings, a 5.02 ERA and two years of medical updates. The Giants are now betting there is still something left in the arm. Maybe there is. Maybe Santos finally gets healthy and finds his command. If that happens, it might sting a little.

But it won’t prove the Mariners were foolish to move on. It will prove they may have been right about the talent and still wrong on the outcome.

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