Mariners have second chance at signing KBO star after losing Hyeseong Kim battle

The Seattle Mariners might have already made the biggest move they're going to make this winter, but it's not as if Josh Naylor's signing is an excuse to call it a day. There's still work to be done, specifically at third base and second base.

This perhaps wouldn't be the case if the Mariners had closed a deal with Hyeseong Kim last offseason. They were reportedly interested in him as he was transitioning over from the Korean Baseball Organization, but Kim instead landed with the Los Angeles Dodgers on a three-year contract. It doesn't resemble a huge miss in retrospect, as Kim only played 71 games for the Dodgers this year and was mostly a defensive specialist in racking up a modest 1.7 rWAR.

In any case, the Mariners have a fresh chance to land a star from the KBO, this time in the person of Sung Mun Song. He will be posted for MLB teams, according to Jeeho Yoo of Yonhap News, with a negotiating window of 30 days.

The Mariners have a second chance to land a KBO star after losing Hyeseong Kim to the Dodgers

Song was relatively anonymous as recently as 2023, which was his third straight season with an OPS in the .600s for the Kiwoom Heroes. Then he busted out in 2024 and 2025, hitting well above .300 and topping a .900 OPS in both seasons.

Song cranked a career-high 26 home runs this year, two more than he had hit across 2021-23 combined. He also has power to go with his speed, stealing 46 bases in 48 tries over the last two seasons.

The Mariners have interest in Song, according to Yankeesource on X. His versatility as someone who can play third base, second base and first base is part of his appeal, though it's his bat that will ultimately determine his usefulness in MLB.

To this end, the best available report on Song — and we should note that we're following MLB.com's lead for how his name is situated — is from Eric Longenhagen of FanGraphs, who isn't overly convinced that his bat will play in MLB:

"He’s been platoon neutral up to this point and has remained productive against the limited exposure to premium velocity the KBO has offered him. But his chase rate spiked to around 30% last year per Synergy, even in an environment where the average heater Song is seeing clocks in around 91 mph, and his aggressive lefty scoop of a swing is accordingly vulnerable to velocity up and away, creating substantially more hit tool risk than a .327 batting average over the last two years might indicate. "

Eric Longenhagen

Because of his baserunning and strong defense, Song doesn't necessarily have to hit a ton to be worth rostering in MLB. Yet Longenhagen concludes that Song batting .230 is more likely than him carrying over as a .330 hitter, which would qualify him as more of a utility guy than an everyday player.

Even so, that doesn't mean the Mariners would have no use for him. They presently have Leo Rivas slated as their primary utility infielder and Song would seem to have more upside than he does, particularly where power is concerned.

With Jorge Polanco and Eugenio Suárez still on the team's radar, Song may not be the Mariners' primary target right now. But unless the Dodgers are going to swoop in again, there isn't a clear reason for why he can't ultimately end up in Seattle.