Much of the focus in Mariners camp will be on the infield. Seattle’s biggest offseason moves — re-signing Josh Naylor and trading for Brendan Donovan — addressed two spots. They lost a couple infielders, Jorge Polanco and Eugenio Suárez, to free agency. It’s the biggest area of turnover on what might be the American League’s best roster.
Naylor and J.P. Crawford are locked into first base and shortstop, respectively. Donovan will be an everyday player. He’s a solid defender at second base and can handle the corner outfield as well, though his below-average speed means he fits better on the infield. Ryan Divish of The Seattle Times writes that Donovan’s early work with infield coach Perry Hill has come at third base.
That’s the simplest solution in the short term. Suárez and Ben Williamson, who was traded to Tampa Bay in the three-team Donovan deal, took the majority of the playing time last season. Of the five players who started games at third base in 2025, only Miles Mastrobuoni remains in the organization. Donovan didn’t get any work at the hot corner last year but logged 269 2/3 innings there between 2022-24. Although defensive grades aren’t especially meaningful in that small a sample, he has above-average marks from Defensive Runs Saved and Outs Above Average.
Donovan’s primary role will largely be determined by the progress of younger players around him. Cole Young had a brutal finish to his rookie season, but he remains the favorite to start at second base. Young is a former first-round pick who hit .279/.388/.432 in the minors and is entering his age-22 season. He remains a very promising young player even though he’s not technically a prospect anymore.
20-year-old shortstop Colt Emerson is even more highly regarded. The 2023 first-round pick combined for a .285/.383/.458 batting line with 16 homers and 14 steals over 600 plate appearances across three minor league levels. Emerson walked at a near-12% clip while striking out less than 18% of the time. He spent the majority of the season in High-A but ripped through Double-A to earn a late-season cameo at Triple-A Tacoma. He played six games there in the final week of the regular season.
Emerson is a consensus top 10 overall prospect at Baseball America, The Athletic, ESPN and MLB Pipeline. The likeliest outcome is that he opens the season at Tacoma with an eye towards a midseason promotion. It’d be a surprise if Emerson breaks camp, but the Mariners aren’t completely closing the door on that as Spring Training opens. “It’s not out of the question that he earns a spot on the team,” president of baseball operations Jerry Dipoto told reporters on Thursday (link via Daniel Kramer of MLB.com). Dipoto praised Emerson’s well-rounded skillset and maturity.
The probable Opening Day infield lines up as Naylor, Young, Crawford and Donovan from right to left. Emerson could get consistent reps against Triple-A pitching while building reps at third base, where he has 111 1/3 innings of professional experience. He’s the heir apparent at shortstop when Crawford hits free agency next winter but presumably wouldn’t push the veteran off the position this year. If Emerson has a monster Spring Training that forces the club’s hand, Donovan could kick back to second base and potentially move Young to Triple-A. That shouldn’t be an issue even if Donovan doesn’t play any second base during Spring Training given his ample work at the position.
Last year’s season-opening second baseman, Ryan Bliss, hasn’t gotten as much public attention. Bliss is older and not nearly as highly regarded as Young and Emerson, so that’s natural, but he’s a former second-round pick who hit .269/.377/.456 with 12 homers and 50 stolen bases in Triple-A in 2024. He unfortunately didn’t get much of an opportunity to solidify himself at the MLB level.
Bliss ruptured his left biceps on a swing two weeks into the regular season. He underwent surgery that came with a 4-5 month rehab timeline. Bliss returned to minor league game action in September and had an impressive week in Triple-A. He may well have reclaimed the second base job from Young to close the regular season had he not sustained a meniscus tear in his right knee that required season-ending surgery. Kramer writes that Bliss is back to full health this spring.
It’s a deep infield that’ll only become more crowded whenever Emerson earns the call. Bliss has a couple minor league options remaining. Leo Rivas also has an option but reached base at a .387 clip in 111 plate appearances last season and made the team’s playoff rosters. They flip-flopped Mastrobuoni and Luke Raley as the last hitter off the bench in October.
They’re both out of options, and it’s difficult to see Seattle carrying both players into the season if all their hitters get through camp healthy. They’ll need bench spots for backup catcher Andrew Knizner and righty platoon bat Rob Refsnyder. Keeping Mastrobuoni and Raley would require them to option both Bliss and Rivas before even considering an Emerson promotion. Dipoto acknowledged the likelihood that someone gets squeezed out at the end of Spring Training, conceding the front office may “have to make some uncomfortable short-term decisions.”
