Mariners Options at Third Base: Solutions at the Hot Corner

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.

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?

The Prodigal Son Returns… Again?

Whilst he finished the season with 49 regular-season homers and one of the most memorable hits in Mariners history, it was not quite the return either Eugenio Suárez or the Mariners would have wanted. After claiming the most coveted bat of the deadline, Suárez struggled for the most part in the back end of the season. This makes a return unlikely, especially with the years and money Suárez will expect, projected for a two-year, $30 million contract. But it is not impossible. It is well documented that his strikeout rate and his streaky play style are expected by whoever signs him. The Arizona Diamondbacks were reportedly looking to move him before he went on his hot streak at the end of 2024. Maybe patience is key. His off-field intangibles mean he will always have value, and that next streak might be just around the corner.

But this is a dangerous game to play with a 34-year-old hitter, especially for a team with limited resources such as the Mariners. He is also a significant downgrade defensively compared to a Williamson, and his profile is not one the Mariners usually covet. However, it cannot be dismissed completely, especially if they believe a reasonable deal can be struck. He is beloved in the city of Seattle, and the feeling appears to be mutual. He is one of the premier power bats in the league and almost hit 50 home runs last season. That cannot be expected again. But another 30–35 season, giving the two prospects another year to develop, could not be the worst solution to this gap in the line-up.

A Big Splash

Trading for a veteran would represent a more aggressive approach to the Mariners’ third base options. While at this moment the trade options for a second baseman seem more plentiful, it is not out of the question for the Mariners to look to the trade pool. Trades are a much more central aspect of the Mariners’ squad-building process, due to Seattle’s location and the lack of financial power to outspend other competing teams. With Polanco on his way to New York, a veteran third baseman comes into play. With one of the deepest farm systems in the league, they have plenty to offer any side and could well be in play for an upgrade via the trade market.

The Mariners are always looking to target players at a good age on reasonable deals. A player who could provide a nice bridge to give their prospects a chance to develop is Alec Bohm. With a contract under $10 million for 2026 and a nice candidate for a longer extension, he is a very gettable piece for Seattle. He’s a very good contact-oriented bat that has good on-base numbers if not too much power. He would certainly add good depth to an already powerful lineup and would not cost them any of their upper-echelon prospects.

International Mariners Third Base Options

Outside of Alex Bregman and then Suárez, the only real options for third on the free agent market come from abroad. International signings represent the most unconventional of the Mariners’ third base options. The standout (and most costly) candidate is Munetaka Murakami of the Tokyo Yakult Swallows. Much has been made of his strikeout percentage and his struggles against fastballs; these are real concerns and will give teams like the Mariners pause. However, the raw power is clear, and he has ample time to develop at only 25 years old. In fact, his ceiling is as high as anyone’s in this year’s free agency class.

The problem for Seattle is that this kind of talent comes at a steep price. And, while geographically on the West Coast, they certainly put themselves in the mix. They also have an obvious history of recruiting from Japan and will be well-known among Japanese players. However, financially, they seem to be on the outside looking in. Scouts project him more as a first baseman or DH long term. With the signing of Naylor, that no longer fits Seattle’s roster construction, which requires an out-and-out third baseman. Murakami is ultimately too risky, too expensive, and lacks sufficient versatility to warrant the contract he will expect.

A Korean Alternative: Song Sung-mun

The options from overseas do not end there. Arguably, the most intriguing and creative solution lies in Korea. Song Sung-mun is another player from the Kiwoom Heroes, the same franchise that sent the three high-profile Korean players currently in MLB, making it a consistent pattern. But despite languishing at the bottom of the KBO every year, Song has been a consistent source of production for the Heroes.

On the back of posting back-to-back elite seasons (2024: (.340/.409/.518, 19 HR) and 2025: (.315/.387/.530, 26 HR)), he will be the cornerstone of the Korean team in the upcoming World Baseball Classic. This profile (and cost) provides a much better fit for what the Mariners require. He does not possess the elite power of Murakami, so his ceiling is much lower. But for 2026, he is a much more well-rounded player who projects to have a higher floor. His on-base numbers are excellent. His average in 2025 was over .300, and his OBP was .387. He is a contact-heavy left-hander with real pop, and his OPS was over .900 this season. Song posted an impressive wRC+ of 151 in 2025, showing his importance on offense. But his value is consistent across various factors of his game, and is what separates him from Murakami.

He is a high-motor, capable defender with speed on the basepaths, stealing 25 bags this year. He possesses infield versatility, playing all in-field positions well, and will come at a much more affordable cost.

While this is a real outside option, it would be great to see Song Sung-mun as an option for the M’s. His ability to play multiple in-field positions means he does not have to block the development of their prospects. This gives flexibility as Crawford comes to the end of his contract. Being an LHH, he can give platoon opportunities to Williamson and Emerson. This would provide a great foundation for years to come.

The Last Word

Ultimately, the Mariners have multiple options at third base, but each one reflects a different organisational philosophy. Choosing Williamson signals confidence in internal development. Turning to Emerson would accelerate the organization’s future timeline. Pursuing Suárez or another veteran prioritizes short-term stability. Trading for a controllable third baseman reinforces their win-now ambitions. And targeting Song Sung-mun would show a willingness to find value where other teams aren’t looking. Time is running out for Murakami and Song to sign with a club after being posted by their respective teams. So their value could depreciate enough to create a good deal.

Whichever direction they choose, the hot corner will define the shape of their offseason.