As a junior at Dongsan High School in Incheon, South Korea, Lee was selected by the Hyundai Unicorns with the 26th pick in the 2nd round (34th overall) of the 2002 KBO Draft. Upon graduation from Dongsan High School, however, he chose to enter Inha University instead of turning pro directly.
In 2007, Lee suffered a case of the sophomore jinx, slipping to 1-2 with a 7.15 ERA in 22.2 innings pitched and earning only 2 holds in 45 games. He spent most of the season in the reserve team of the Unicorns.
Lee earned a spot in the starting rotation for the 2008 season. In his first year as a full-time starter, he ended the season with a record of 6 wins and 11 losses and a 4.58 ERA in 120 innings pitched.
In 2009, Lee had his best pro season. As a full-time starter, he was 4th in wins (13), 5th in innings pitched (170.0), 10th in strikeouts (120) and 11th in ERA (4.18), all of which were career bests. However, on December 30, Lee was traded to the Doosan Bears for pitcher Keum Min-Chul and one billion won, involved in the Heroes' postseason blockbuster trades.[1]
In 2010 Lee started his first season in the Bears as a starter, but was demoted to the bullpen in the middle of the season due to finger injuries and ongoing trouble with his command. He finished the season with a 4.75 ERA in 77.2 innings pitched and a 3-6 record. In the postseason, however, Lee played a major role in the Bears' bullpen, going 1-0 with a 0.96 ERA in 7 games, compiling 11 strikeouts in 9.1 innings pitched.
In 2011 Lee spent the entire season in relief, compiling a 3–5 record with four saves, six holds and a 4.82 ERA in 74.2 innings of work spread over 50 appearances.
