MLBTR has the details of who he is, the slight differences versus Japanese posting, etc.
The Kiwoom Heroes of the Korea Baseball Organization have agreed to post infielder Sung-mun Song, reports Jeeho Yoo of Yonhap News. The KBO posting window is 30 days (unlike the 45-day period for players coming over from Japan’s NPB). MLB teams will officially be able to negotiate with Song, whom Yoo adds has hired ISE Baseball to represent him, on Saturday morning. He’ll need to sign by 5:00 pm Eastern on December 21 or remain with the Heroes.
Song, 29, is a left-handed hitter who has played all nine seasons of his career with that club. He posted a sub-.700 OPS every year between 2021-23 but has taken a leap forward at the plate over the past two years. Song hit .340/.409/.518 last year and is coming off an equally impressive ’25 campaign. He popped a career-best 26 home runs with a .315/.387/.530 slash across 646 plate appearances.
And, here's how he is seen as fitting in MLB:
Eric Longenhagen of FanGraphs gave Song a 45 FV grade, which is commensurate with a mid-level prospect from the typical organization’s top 30 list. … The biggest question is his pure hitting ability. Longenhagen writes that Song has shown a bit of a propensity to chase outside the strike zone and has an uphill swing path that can leave him vulnerable to pitches up in the zone, especially those on the outer half. …
Song has some defensive flexibility, but an inability to play shortstop limits his value as a utility piece. He’s primarily a corner infielder who also has almost 1300 innings at second base. …
Cost?
A signing team would owe a posting fee to the Heroes on top of whatever is guaranteed to Song. That’s proportional to the contract value: 20% of the first $25MM, 17.5% of the next $25MM, and 15% thereafter. It’d be surprising if Song tops $25MM, so the likeliest outcome is that the release fee will be 20% of the guarantee.
MLBTR adds that he will likely be the only KBO player to post this year.