Detroit ? Mike Sweeney knows his major-league career might be over. The Oakland Athletics released the 35-year-old first baseman-designated hitter Tuesday after he struggled to return from operations on each knee.

Sweeney, a 14-year veteran who spent all but this season with the Kansas City Royals, was limited to 42 games this year because of knee injuries. Doctors have told the five-time All-Star he needs surgery on both knees, and the recovery time is six to nine months.

Sweeney has a .299 career batting average with 199 homers and 849 RBIs in 1,324 games. After signing a minor-league deal with the A’s before spring training, he batted .286 this season with two home runs and 12 RBIs.