Unicorns and tossed 5.2 scoreless innings of four-hit ball. However, Yang struggled with his command and was never able to regain it to the level he had earlier in the season. At the end of May, Yang was eventually demoted to the reserve team of the Tigers. In August, the young left-hander came back to the Tigers first-team roster and pitched in relief of the Tigers' starters in the second half of the season. On September 29, 2007, Yang recorded his first professional win against the Hanwha Eagles in Daejeon, pitching five innings of two-hit, one-run ball as a starter. Yang finished his rookie season with a record of 1–2 and an ERA of 4.17 in 49.2 innings pitched, appearing in 31 games as a utility pitcher. Yang had a disappointing sophomore season in 2008, slipping to 0–5 with a 5.83 ERA. He started the season as a starting pitcher, but struggled through five appearances with an ERA of 7.00 and was eventually relegated to the bullpen. Though frequently sent to the mound as a starter to fill a temporary void in the rotation during the season, Yang mainly pitched in relief for the Tigers, garnering 5 holds as a setup man. In 2009, Yang had a career year. He was 9th in wins (12), 5th in ERA (3.15), 4th in strikeouts (139) and 12th in innings pitched (148.2), all of which were career bests. On August 11, he had one of his best performances of his pro career, hurling 7.1 shutout innings in which he only allowed 5 hits with no walks and struck out 10 batters against the Lotte Giants. On November 14, Yang pitched as the starter for the Tigers in the 2009 KBO-NPB Club Championship game against the Yomiuri Giants. In that game, he allowed only three hits and one run and racked up 6 strikeouts in 5.2 innings. In 2010, Yang's ERA rose over a full point to 4.25 and gave up the second-highest number of hits in the KBO league with 169, resulting in a .272 batting average against. However, he had four more wins than the previous year, posting a 16–8 record and striking out 145 batters. Yang was runner-up in wins and third in strikeouts among the KBO pitchers in the 2010 season. He pitched his first career complete game shutout against the Samsung Lions on June 2. In 2011, Yang struggled,