While attending Yonsei University, Na was considered the best hitting pitcher in the South Korean collegiate baseball league. As a freshman in 2008 Na batted a team-leading .329 with 11 RBI and posted a 3–1 record and a 1.70 ERA with 83 strikeouts (runner-up in the collegiate league) in 74.0 innings pitched.
As a senior in 2011, Na struggled a bit, posting a career-worst 3.76 ERA, but fanned 68 batters. In September 2011, Na was called up to the South Korean national team again for the 2011 Baseball World Cup held in Panama.
Na Sung-bum originally was drafted by the NC Dinos as a pitcher, but changed his position to outfielder after a suggestion from Dinos manager Kim Kyung-moon. In 2012, he played 94 games in the farm league, finishing with a .303 batting average, 16 home runs, and 67 RBI. He won RBI leaders and Home Run Title.
In his first full season the next year, when he hit 14 home runs with a .243 batting average and 64 RBI, Na was runner-up in the KBO Rookie of the Year voting, behind team fellow Lee Jae-hak.
Na broke out in 2014 when he hit 30 home runs, batted .329 and drove in 101 runs, and quickly became a favorite of the Dinos' organization and a household name among the team's fans, voted the top competition at the KBO All-Star voting. He garnered 968,013 votes from fans and another 193 votes from KBO coaches and fellow players to lead the 22 All-Star starters.[1]
Na maintained his status as one of the league's elite power-hitting outfielders in 2015, when finished ninth in the league with a .326 batting average, drove in 135 runs (fourth in the league) and slugged 28 home runs (seventh in the league).
Despite getting off to a hot start on the 2016 season, cold streaks in the second half of the year ruined chances of Na putting together a great year. However, he finished the year with respectable offensive numbers, finishing the year with 22 home runs, 113 RBI and a .309 batting average.
After the 2021 season, Na signed a six-year contract for ₩15 billion the KIA Tigers.[3]
Baseball fans paid attention to what Na Sung-bum would look like in his return season after the 2019 season, which ended the season early due to a major injury, and he showed his robustness by playing a full-time season. He played in 130 of the 144 games of the 2020 season, ranking fourth among the team's players. He played a lot as a designated hitter because it was his first season back from injury, but he went one step further in the next 2021 season and played mainly as a right fielder, but again achieved all games and played the most games in the team. In the 2022 season, he still played 144 games as a full-time right fielder. If he was seriously injured like that once, he could have saved himself, but he is still a good hustler.[4]
