SEATTLE — For most of this offseason, it's been thought that the Seattle Mariners' open third base position would come down to a battle between two young players: Colt Emerson and Ben Williamson.

On Monday, the Mariners both simplified and complicated that competition.

Seattle acquired 2025 All-Star utility player Brendan Donovan from the St. Louis Cardinals in a three-team trade that also involved the Tampa Bay Rays.

The Mariners sent switch-pitching prospect Jurrangelo Cijntje, outfield prospect Tai Peete and a Competitive Balance Round B draft pick to the Cardinals - and Williamson to the Rays.

Despite Donovan playing mostly at second base, trading Williamson seems to indicate that the former will play mostly third. If that's the case, Cole Young will be given the runway to be Seattle's de facto starting second baseman.

However, one of the benefits to acquiring Donovan is his positional versatility. The 29-year-old has played every position except center field and first base the last two seasons. He registered 52.2 innings at third base in '24 but didn't man the hot corner in '25.

This flexibility allows the Mariners to move Donovan around the field to fit its lineup as it seems fit.

Emerson may not be competing with Williamson for the open third base spot anymore but he'll still play to earn a spot on the Opening Day roster in spring training.

"I think (we're looking for) execution of what their identity is," Seattle general manager Justin Hollander said during Day 2 of the team's FanFest event Sunday (before the Donovan move). "Even in a spring training environment, it's really important. Every year when we go into the spring training initial meeting with the staff, I put in like a warning out to everyone that this environment will fool you every year. Somebody will hit 1.000 and someone will hit .000 and it doesn't mean anything once we get out here (at T-Mobile Park). ... Definitely not gonna focus on the statistical performance. ... (For) position players, how do they look physically? How are they moving? All that stuff are things we're focused on."

Emerson has already received every vote of confidence a prospect can receive from a team except for making the major league roster. He began 2025 with the High-A Everett AquaSox and ended the year with the Triple-A Tacoma Rainiers. He was also on the team's postseason taxi squad.

The 20-year-old is a universal top-10 prospect in baseball (No. 9 per MLB Pipeline). Donovan's addition might not make his math as clear as it was before. But it still leans towards a matter of when, not if, Emerson debuts in the majors in '26.

"My message to him would be 'go have fun and be yourself,'" Hollander said. "I'm not really worried about how he'll handle the spotlight or any external thoughts about 'when is his time and when's not his time.' ... People have always told me, when I was first starting that the prospects that are this good just tell you when they're ready. You can decide on your own but that doesn't really do any good. They just tell you. My guess is he'll just tell us. I have no idea if that'll be on March 26 or on July 1 or (March 26, 2027). It'll be up to him. ... He's a special player with special tools and special makeup, too."

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