The Seattle Mariners ended the season with one of the deepest rosters they have ever put together, finishing agonizingly short of a maiden World Series. This was the result of an aggressive trade deadline in which the front office uncharacteristically chased rental bats to maximise the window in front of them. It proved a successful gambit, signalling a sense of urgency not previously associated with Jerry Dipoto and Justin Hollander. The corner-infield additions gave Seattle real depth and propelled them to a division title. That urgency carried into the winter, as they made the first major move of the offseason, securing Josh Naylor on a five-year deal, and adding to the bullpen via trade. Third base, however, remains the biggest question among the Mariners’ offseason options.

The hot corner has been a long-term uncertainty for the Mariners. Once again, it stands out as the primary concern as they look to repeat their success. Below, we explore the possible solutions to the hot-corner problem and the routes available to the front office as Seattle aims to go back-to-back in the American League West.

The Mariners’ Options at Third Base Next Season
In-House Stability

Among the Mariners’ options at third base, internal development remains the most likely path. Within their system, they have two prospects they believe are ready to make the jump. Ben Williamson — the more likely Opening Day starter — played 85 games, covering pretty much the entire first half of the season until Eugenio Suárez was acquired at the deadline. He does not project as an above-average bat. This was evident throughout the season, barely getting above a .600 OPS. However, he is a plus defender with excellent range and a dependable arm. At the time he was sent down, he led AL third basemen in DRS and still finished the year sixth despite spending months in the minors.

Jul 5, 2025; Seattle, Washington, USA; Seattle Mariners third baseman Ben Williamson (9) hits an RBI double against the Pittsburgh Pirates during the sixth inning at T-Mobile Park. Mandatory Credit: John Froschauer-Imagn Images

Infield defense was a cause for concern in the postseason, with only Naylor really seen as an above-average defender from their starting infield. The lack of range was concerning and showed up multiple times in big moments. So when Williamson can cover the left side of the infield and support J.P. Crawford, that is a noticeable upgrade. He also seemed to develop a bit more pop when he went back down to Triple-A Tacoma in the latter stages of the minor league season (.314/.392/.462/.854). With the Mariners’ pitching seemingly focusing heavily on high ground ball rates, having a plus glove at third base becomes preferable. Williamson gives you that in spades. They will have to hope he can be at least serviceable with the bat, or make additions that allow him to be hidden at the bottom of the order.

Williamson provides as high a floor as you can ask for from a prospect. He gives you stability and defense at the hot corner right now, with the chance for development in the future. The slightly more exciting option is Colt Emerson.

The Higher Ceiling: Colt Emerson

The highest prospect in the Mariners’ system — and a top-10 prospect in the country — Emerson has primarily been a shortstop, but his future, and certainly his entry point into the team, will be at third. Playing for three teams in the minors, Emerson ascended from High-A Everett all the way to the playoff taxi squad in 2025. In just six games at Triple-A, he put up an OPS of 1.171. It is an extremely small sample size. Still, the way the Mariners handled his development in 2025 suggests he will earn a shot at the Opening Day job. Emerson has a very advanced approach for his age and possesses much higher upside than Williamson with the bat. He possesses real on-base skills (.383 OBP) and room to develop his power. We saw this with his 16 home runs in 2025 across three minor league teams.

One of R Favorite home runs of 2025: Colt Emerson going deep in his Triple-A debut! pic.twitter.com/XpY8fQHlYn

— Tacoma Rainiers (@RainiersLand) November 25, 2025

As a bat-first infielder, Emerson juxtaposes interestingly with Williamson, and it will be fascinating to see which skill set the Mariners prefer. It probably lines up with Williamson getting the Opening Day role, if this is indeed the route they choose, with Emerson getting a look around May. With Jorge Polanco signing with the New York Mets on a two-year, $40 million deal, it opens up the likelihood of Cole Young being the 2026 starter. If this plays out, they might want to avoid having two prospects at two such important positions on the infield. So what alternative solutions are available if they want to pivot elsewhere?