Cleveland pitcher Rafael Betancourt has tested positive for a banned substance and has been suspended for 10 days.
Betancourt, on the disabled list with a shoulder injury, is disputing the claim and will ask the players' association to file a grievance.
"I am very angry and disappointed with the decision to suspend me," he said.
Betancourt is the sixth player to be suspended under MLB's new policy, which began in March. There have been 77 minor leaguers suspended to date.