In August 2006, Yang led his team to runner-up at the 36th Phoenix Flag National High School Baseball Championship where he was named best pitcher, going 1–1 with an ERA of 0.90 and leading the tournament with 32 strikeouts.

Upon graduation from Dongsung High School, Yang was selected by the Kia Tigers in the 2nd round (1st pick, 9th overall) of the 2007 KBO Draft.

[1] He made his KBO debut on April 7, 2007, against the LG Twins at Jamsil Baseball Stadium in Seoul, coming from the bullpen, but allowed a solo home run in one inning pitched.

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.

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.

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 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.

[5] (It was reported that the Minnesota Twins or the Texas Rangers were possibly the highest bidders with a bid estimated at $1.5 million, though the exact details were never disclosed.

On July 2, 2015, Yang threw a one-hit shutout against the Doosan Bears, striking out 10 and allowing two walks.

[12] On February 12, 2021, Yang signed a minor league contract with the Texas Rangers organization that included an invitation to Spring Training.

[17] After posting a 5.60 ERA with 42 strikeouts through 10 games for Round Rock, the Rangers selected Yang's contract on August 24.

[23] On June 6, 2024, Yang recorded his 2,000th career KBO strikeout, joining longtime Hanwha Eagle Jin-woo Song as the only pitchers to achieve the feat.