Mariners bullpen contains a huge breakout waiting to happen in 2026

Each offseason, the part of the roster that typically sees the most activity for any MLB team is the bullpen. Even with the wealth of talent in Seattle, there's always a need for arm depth, especially at the front of the bullpen where players are pretty expendable. Furthermore, the volatile nature of relief pitching means even the most unsuspecting player could end up being surprisingly impactful.

The Mariners haven't stopped taking fliers on pitchers with some upside, but for the most part, their core relief unit is set in stone. Andrés Muñoz will be closing games and preceding him will be either Matt Brash or Jose A. Ferrer. Gabe Speier and Eduard Bazardo can handle medium leverage if needed as well, depending on the handedness of the batters due up.

This is already more depth than other organizations could ever hope for. Nonetheless, Seattle still has another potential ace up their sleeve. Based on his work in the big leagues so far, that title may be surprising, but more forward-looking statistics suggest that his best is yet to come.

Based on pitch modeling data, Carlos Vargas has the stuff to be another elite reliever for the Mariners

Vargas had quite the workload in 2025, pitching to an ERA of 3.97 over 77 innings. There were quite a few unrefined aspects to his game, especially when it came to missing bats. His whiff rate of 18.9 was in the bottom decile of qualified pitchers, as was his strikeout rate of 16.3. He made up for it with an exceptional ground ball rate of 57.1 but the batted balls that did make it in the air landed as home runs 14.9 of the time.

His rookie year wasn't particularly notable when it came down the numbers on paper but as a young player, his future is what's most exciting. To model the effectiveness of pitches based on intrinsic characteristics, FanGraphs uses a metric called Stuff+ that returns a normalized value of how it stacks up against the rest of the league. Location+ is a similar statistic that looks to measure command.

According to this, Carlos Vargas has some of the nastiest stuff in the bullpen. Each of his four pitches grade out as above average with his slider (118) and sinker (116) taking the top two scores in his arsenal (his changeup received a Stuff+ of 120 but he threw it just 21 times). Furthermore, Pitching+, which is a more holistic overview of a pitcher's complete process based on a similar modeling system, grades him at 113, tied with Gabe Speier as the best score of any qualified Seattle reliever.

At first, this seems to conflict with the data we have for last season, especially since his sinker was his only pitch worth positive run value. However, it's important to acknowledge that pitch modeling only captures how effective a pitch should hypothetically be based on aspects like velocity and movement, both of which Vargas does pretty well.

One of the most unique aspects of Vargas is the relatively small difference in velocity between his sinker (97.6 mph), cutter (95.2 mph), and slider (90.3 mph). Those who throw fastballs in the upper 90s don't typically see much additional velocity on their slider. For example, Andrés Muñoz averaged 97.8 mph on his sinker and just 86.1 mph on his slider, a spread of more than 10 mph.

This is both a blessing and a curse. A hard slider can be effective but currently, it blends in too much with his cutter in terms of shape and velocity. This means a batter that may have been late on cutters earlier in the at-bat would be right on time for the slider.

Like many of his other teammates, refining his arsenal and potentially adding a new pitch could be the key to a rebound season in 2026. If the pitch modeling data looks good, then his shortcomings must lie elsewhere. Getting clearer separation between the many outstanding weapons in his arsenal could be the first issue to fix.

Additionally, sequencing, command, and just bad luck are all factors that could be preventing his true potential from shining through the surface. As a whole, Seattle's bullpen still has some uncertainties to work through. For Carlos Vargas, the biggest uncertainty is discovering what it will take for him to finally unlock his final form.