WATCH: Which Relievers Could Mariners Pursue in Free Agency?

Even with Andres Munoz and Matt Brash set to return as part of a stellar bullpen in 2026, the Mariners could still use reinforcements to further bolster the group. Emerald City Spectrum reporter Callaghan Bluechel looks at five relievers who could take Seattle to the next level, including a familiar face returning in a setup role in Edwin Diaz.

While the Seattle Mariners have historically relied on trades to supply much of their bullpen core, there are still plenty of relievers on the free agency market that should at least pique the team’s interest. Some of these relievers are pricey, others cheaper; some are squarely elite while others have more question marks on their 2026 season. The end of the 2025 year showed that a deep playoff run is aided when the bullpen is filled with quality, trustable arms, so the team should definitely seek to augment the ‘pen.

The Reunion: Mets RHP Edwin Díaz.

Former Mariners fireballer Edwin Díaz, who set a Mariners record for saves in a season with 57 in 2018, has made quite a career for himself with the New York Mets. Despite a bad year in 2019, he has boasted an elite stat line since: 2.36 ERA, 2.15 FIP, 0.977 WHIP, 0.6 home runs per nine innings, 14.6 strikeouts per nine innings, and 3.2 walks per nine innings. Both his four-seamer and slider are some of the best pitches in the game.

He is as close as a free agent reliever can be to a surefire thing, but with that pedigree comes a price. Spotrac estimates his average annual value (AAV) at $18.3 million, but since he is expected to decline the Mets’ $22 million qualifying offer, any potential contract could reach beyond that and the expectation is that he will sign a multi-year deal. Given that any big splash from the M’s free agency-wise would probably be for a hitter, I wouldn’t hold my breath expecting the trumpets in T-Mobile.

The Submarine: Mets RHP Tyler Rogers.

One of the most unique pitchers in baseball is Mets reliever Tyler Rogers, who delivers the ball from an angle of negative 61 degrees. Despite neither his sinker nor slider reaching 90 miles per hour, batters can’t get a handle on either of them: his 61.6 percent ground ball rate is higher than 98 percent of MLB pitchers while his 33.1 percent opposing hard hit rate is better than 95 percent of his peers. All of this brought him to a 1.98 ERA, 2.88 FIP, and 0.944 WHIP in 77 ⅓ innings pitched.

His price tag is smaller than Díaz’ at an estimated $11.3 AAV, but that is still fairly large for a reliever, and Rogers will be 35 in 2026. Still, his submarine style would throw hitters off from the rest of the Mariners bullpen, and he has shown an ability to be effective across seasons.

Another NL East Arm: Braves RHP Raisel Iglesias.

Also in his mid-30s and still effective, Raisel Iglesias boasted a 3.21 ERA, 3.31 FIP, and 0.995 WHIP over 67 ⅓ innings in the 2025 season. Of his four-pitch mix, Iglesias relied more on his sinker and less on his slider than in previous seasons, as it seemed batters were catching up to the slider a little bit more. The Mariners’ pitching lab has shown its ability to work with sliders, four-seamers, and sinkers, so there is a good chance for him to fit into Seattle’s ‘pen - although if the M’s need someone more unique compared to their other relievers, they might look elsewhere.

Age, however, is more of a concern with Iglesias. Both his fastballs lost notable velocity in 2025, and since he is turning 36, his heaters won’t get any quicker. He is expected to seek a two-year contract this offseason and Spotrac estimates his AAV at $8.8 million, but there’s a fairly wide range around that.

The Elder Statesman: Angels RHP Kenley Jansen.

Despite being in his age 37 season, Kenley Jansen continued to perform, with a 2.59 ERA and 0.949 WHIP in 59 innings pitched while striking out 8.9 batters per nine innings and walking 2.9 per nine innings. But there are a whole lot of indications that Jansen benefitted from serious luck in 2025, starting with a .196 batting average on balls in play (BABIP). Both pitchers and hitters tend to revert to a league average BABIP of around .290, so an exceptionally low BABIP indicates pitching overperformance. In addition, batters’ hard hit rate against Jansen jumped from 37 percent in 2024 to 44.6 percent in 2025, while his 8.9 strikeouts per nine - while still good - marked the first time in his career that the stat dipped below 10.

While his high arm angle and cutter-heavy approach set him apart from other pitchers around baseball, a potentially high price tag (estimated at $13.7 million AAV according to Spotrac) is another potential red flag about Jansen.

The Potential Breakout: Blue Jays RHP Seranthony Domínguez.

Of all the relievers on this list, Domínguez is the least proven at an elite level, but there are clear signs that he has elite potential. Pitching for the Orioles and Blue Jays in 2025, he had a 3.24 ERA, 3.47 FIP, and 1.344 WHIP over 62 ⅔ innings with 11.3 strikeouts per nine innings and 5.2 walks per nine innings. Clearly, his walks are a problem, but if he cut his walk rate in half, he would have a 2.61 FIP and his WHIP would be 0.989.

Now, that may sound like something in the vein of “if wishes were fishes, the sea would be full,” but his wildness is mainly confined to his two fastballs, both pitches that the Mariners lab works well to improve. Domínguez’ sweeper, one of the best in the game, found an excellent complement in an elite splitter. If the M’s could find a sweet spot for Domínguez around 40 percent sweepers, 40 percent splitters, and 20 percent four-seamers, they could find the reliever breaking out from good to great.

2026 will be Domínguez’ age 31 season, reducing age as a concern compared to someone like Jansen or Iglesias, and an estimated $10.7 million AAV indicates a price range within reason for Seattle. The “ifs” in his profile mean that his floor and ceiling are relatively far apart, but with the pitching lab’s fastball ability, he does appear to be someone the team could work with.