Born on August 29, 1996 in Seoul, South Korea, Sung-Mun Song was drafted by the Nexen Heroes in the fifth round of the 2015 KBO Draft, the 49th overall pick, selected out of Jangchung High School, a nationally-competitive
baseball school. He appeared in a handful of games for Nexen in May, but barely accrued playing time, getting into 7 games both years and receiving 12 at-bats. He spent the rest of the 2015 season, as well as all of 2016, in the KBO Futures League.
In 2017, the 21-year-old was called back up, got into a few more games in three separate stints with the team, appearing in a few games at the end of April and beginning of May, in mid-July to mid-August, and then again in a handful of games at the end of the season in late September and October. All in all, Song appeared in 38 games and logged 90 at-bats, hitting .273/.360/.338 with 0 doubles, 1 triple, 1 home run, 0 stolen bases in 1 attempt, and drew 10 walks to 16 strikeouts. His performance was not exceptional, per se, but he held his own and hit well enough that he began the 2018 season on the major league club.
The 2018 season was a breakout for Song, as he appeared in 78 games and logged 211 at-bats, hitting .313/.381/.502 with 19 doubles, 0 triples, 7 home runs, 2 stolen bases in 6 attempts, and drew 24 walks to 49 strikeouts. Song was unable to build on that in 2019. Appearing in 103 games for the now Kiwoom Heroes, the 22-year-old hit .227/.269/.328 with 12 doubles, 5 triples, 3 home runs, 2 stolen bases in 3 attempts, and 19 walks to 53 strikeouts.
Song missed the 2020 season fulfilling his military obligations. He missed part of the 2021 season while doing so as well, limiting him to just 66 games when he was able to get back on the field in early July. In those 66 games, he hit .249/.320/.371 with 10 doubles, 1 triple, 6 home runs, 0 stolen bases, and 25 walks to 42 strikeouts.
Song had similar seasons in 2022 and 2023 as well. In 2022, he appeared in 142 games and batted .247/.302/.371 with 21 doubles, 4 triples, 12 home runs, 0 stolen bases, and 45 walks to 65 strikeouts, while he hit .263/.325/.358 in 104 games in 2023 with 16 doubles, 3 triples, 5 home runs, 1 stolen base in as many attempts, and 39 walks to 38 strikeouts.
In 2024, Song got married, was named captain of the team, and adjusted his approach at the plate to pull the ball more. One or all of these things helped him bloom into the second-best player in the KBO, second only to Do-Yeong Kim’s historic season. Appearing in 142 games for the Heroes, Song hit .340/.409/.518 with 29 doubles, 4 triples, 19 home runs, 21 stolen bases in as many attempts, and 64 walks to 82 strikeouts. The 28-year-old replicated that success in 2025 and was once again one of the most valuable players in the league, appearing in 144 games and hitting .315/.387/.530 with 37 doubles, 4 triples, 26 home runs, 25 stolen bases in 27 attempts, and 68 walks to 96 strikeouts.
Song, a left-handed batter, stands open at the plate, holding his hands high and angling his bat head at 10:30, leaning it towards the pitcher. He loads up with a big leg kick, planting and swinging a long bat. His power comes from the torque from his upper body rotation, but despite the visual of what looks like a full-effort all-or-nothing swing with his entire body’s momentum taking him out of the box, Song does not sell out much for power. Since 2024, the start of his power surge, his swinging strike and strikeout rates have mostly remained static and his contact rate dropped only minimally, from a 85.1% in 2021-2023 to 81.4% in 2024-2025. Pulling the ball more has been the key to his increased power, as his Soft Hit % has gone down while his Hard Hit % has gone up
Defensively, Song has experience playing first, second and third base. He is generally not an aggressive defender, letting the ball come to him rather than going to the ball, but thanks to his quick-twitch athleticism and above-average speed and range, he can get to plenty of balls, and make throws from a variety of angles on the ground, on his knees, and on the run. He has an accurate arm but his arm strength is stretched at third base and better suited at second.
Song signed a six-year extension with the Heroes prior to being posted, but made his intent to be posted known to the club during their contractual negotiations. While he initially was weary of being posted, he was convinced by former teammate Ha-Seong Kim. Kim, along with Jung-Hoo Lee and Hye-Seong Kim, were all teammates at different points with each other and Sung-Mun Song on the Heroes between 2015 and the present.
