Bueno started his two-game suspension in the Royals' series finale against the White Sox that stemmed from an ejection in his only Major League appearance before this season.
While with the Braves on Aug. 13, 2008, the lefty threw a fastball over Cubs outfielder Alfonso Soriano's head in the ninth inning at Turner Field and was immediately ejected.
He was issued a three-game suspension the following day, but also optioned to Triple-A. He didn't return to the Majors until this season and has appeared in 10 games for the Royals.
Bueno, 31, appealed the suspension and got it trimmed to two games. He is eligible to return Wednesday in Minnesota.