Yoon is a 6 ft 0 in, 180 lb right-handed pitcher. With a three-quarters delivery Yoon throws a fastball at 90-92 mph (tops out at 96 mph), a change-up, an occasional curveball, and a hard-breaking, mid-80s slider. With a shoulder injury his fastball dipped into high-80s, and he converted to relief during the 2013 season.
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Selected by the Kia Tigers with the 1st pick in the 2nd round of the 2005 KBO draft, Yoon made his pro debut with the Tigers on April 2, 2005. In his rookie season, he showed signs of promise, pitching 84 innings in 53 games with a 4.29 ERA as the Tigers' primary setup man.
In 2007, Yoon joined the starting rotation due to the Tigers' ace Han Ki-Joo's transition to a closing pitcher. However, Yoon was not so successful, going 7-18 with a 3.78 ERA as a starter. While his ERA was decent, he had poor run support in 18 of his losses, the most in the 2007 season. This gave him the nickname "The Unfortunate Ace".
In 2008, Yoon emerged as one of the most consistent pitchers in the KBO league, going 14-5 with a 2.33 ERA and 119 strikeouts in 154.2 innings pitched. He won the ERA title and finished runner-up to Kim Kwang-Hyun in wins.
In March 2009, Yoon competed for the South Korea national baseball team in the 2009 World Baseball Classic, where he went 2-0 with a 1.13 ERA and 13 strikeouts in 16 innings pitched, appearing in 4 games. He started against Venezuela in the semifinal game, and led South Korea to a 10-2 victory. Yoon baffled the South American major league all-star squad, allowing only two runs and seven hits in 6.1 innings pitched.
In the beginning of the 2009 KBO season, Yoon became the Tigers' closer again as Han Ki-Joo was put on the disabled list. As a closer, he posted 7 saves with a 2.45 ERA. Yoon returned to the starting rotation but was put on the disabled list for a month. In July, he returned from the injury and won all of his 7 decisions as a starter. However, he had the worst pitching performance in his pro career on September 5, allowing 10 runs in just 3.1 innings against the Doosan Bears, and was then sidelined with a shoulder injury for the rest of the season. Yoon finished the season with a record of 9-4 with 7 saves, an ERA of 3.46 and 117 strikeouts in 119.2 innings pitched which didn't enable him to qualify for the ERA title.
Yoon was named Most Valuable Player (MVP) for the 2011 season. He received the KBO's highest honor for leading the league in four pitching catagories, marking a 2.45 ERA, 17 wins, 178 strikeouts, and a .773 winning percentage in 172 1/3 innings. He is the first pitcher to stand at top of four categories since Korean pitching legend, Sun Dong-yeol accomplished the feat in 1991.
A free agent after the 2013 season, Yoon announced his intentions to play in Major League Baseball. According to unconfirmed reports, Yoon has agreed to a three-year contract, worth US$5.75 million, with the Baltimore Orioles. On February 17, 2014, Yoon has passed his physicals and officially signed by the Orioles.