Sierra hit .179 with one double and four RBI in just 28 at-bats this season. The 40-year-old spent six weeks on the disabled list after rupturing the biceps tendon near his left elbow and never really got much playing time after that in his role as a pinch-hitter.
He also had a strained quadriceps muscle in spring training that kept him from joining the team for Opening Day. He has 306 home runs and 1,322 RBI in 20 major-league seasons.
Sierra was one of several veteran hitters added in the offseason, part of GM Terry Ryan's plan to infuse more pop and experience into the Twins' lineup. Now midway through the season, the Twins have jettisoned Sierra and third baseman Tony Batista and designated hitter Rondell White is on the disabled list and has struggled mightily.
The youth movement that followed helped the Twins rebound from seven games below .500 in mid-May to eight games over .500 at the All-Star break.
The Twins said they will make an additional roster move to replace Sierra on the 25-man roster prior to Thursday night's game against Cleveland.