The team won the gold medal at the inaugural Asian Youth Baseball Championship, and Na was named MVP of the competition, appearing in all the games as a pitcher.
While attending college, Na was considered one of the top sluggers in the South Korean collegiate baseball league, winning home run titles in 2006 and 2007.
Na fell into a slump, showing a weakness against breaking balls, and was demoted to the second (reserve) team of the Tigers at the end of April.
In 2009, Na became a fixture at left field for the Tigers as starting outfielder Lee Yong-Kyu was sidelined due to an ankle injury in the beginning of the season.
Earlier in the game, when Kia was trailing 5–1 in the sixth inning, Na smacked a two-run home run off Wyverns' reliever Lee Seung-Ho.
Na's big bat in Game 7 helped earn him MVP honors in the Korean Series, although Tigers' starting pitcher Aquilino López arguably deserved the award.