Seattle Mariners Free Agency: Another Third Base Option Hits Market

The Seattle Mariners have yet to hire a manager this offseason, but other offseason business is set to continue as it does each year.

The Mariners have already declined and exercised club options on several players and free agents will be able to sign with teams beginning 2 p.m. PT on Monday.

When free agency begins, Seattle will be in the market for at least a left fielder or a third baseman.

The Mariners are expected to extend a qualifying offer (one-year, about $23 million) to left fielder Randy Arozarena, who's likely to decline and pursue a bigger and long-term contract in a week free agency class.

This will leave either Brendan Donovan or Michael Arroyo as the likeliest in-house candidates to replace Arozarena for 2027. However, the latter underwent offseason elbow surgery that will keep him out until April.

This makes Donovan the likeliest candidate to play left field for Seattle in '27, which will leave third base and shortstop vacant with veteran shortstop J.P. Crawford also set to hit free agency.

There's few third basemen available that inspire confidence as everyday starters. The Mariners have already been linked to intriguing option Teruaki Sato, who was posted by the Hanshin Tigers of Japan's Nippon Professional Baseball and is also capable of playing the corner outfield spots.

Another international third baseman was also recently posted and will be an option for Seattle to pursue.

According to a post on "X" from KBO in English (@KBO_ENG) on Saturday, the Hanwha Eagles of the Korean Baseball Organization have officially posted third baseman Roh Si-hwan and he is available to sign with all 30 MLB clubs. He'll have 30 days to sign with an MLB team.

Si-hwan, 25-years-old, has played eight seasons with the Eagles from 2019-2026. He was a part of Team Korea in the 2022 Asian Games, where Korea won the Gold medal. He also competed for his native country in the 2026 World Baseball Classic.

In 2026, Si-hwan slashed .283/.360/.505 with an .865 OPS in 127 games and hit 21 doubles, two triples and 29 home runs with 96 RBIs. He posted five-straight seasons with at least 20 homers.

Si-hwan would satisfy the team's need for a third baseman and a right-handed hitter, and would likely require less money to sign than Sato. However, as is the case with Sato, Si-hwan's strikeout-to-power numbers raise questions. Si-hwan had a 25.7% strikeout rate in 2026 to go with his 29 home runs.

Seattle has explored signing hitters from the KBO before. In 2024, the Mariners pushed to sign utility infielder Hyseong Kim before he ultimately signed with the Los Angeles Dodgers. Kim's been up-and-down between the Dodgers' Triple-A affiliate and major league roster since and has slashed .271/.318/.361 with a .679 OPS in 114 games. He's hit nine doubles, two triples and four home runs with 28 RBIs and has stolen 18 bases in 20 attempts.

Kim signed a four-year, $12.5 million deal. If that's in line with what Si-hwan earns, that would fit well within the M's expected $30-35 million in available payroll, even including the 20 percent posting fee owed to the Eagles with that hypothetical contract.

However, if the Mariners are interested in Si-hwan, it seems like they'll have to contend with their archrivals.

KBO in English also posted that the Houston Astros are rumored to have interest in Si-hwan.