The Major League Baseball (MLS) Players Association formally sent an appeal against Alex Rodriguez's 211-game suspension to an independent arbitrator.
New York Yankees player Rodriguez Monday was among 13 players penalised for involvement in doping. The other 12 players accepted 50-game suspensions, but Rodriguez said he planned to fight, reports Xinhua.
Rodriguez's punishment was scheduled to begin Thursday, but he is allowed to keep playing until the grievance is heard by arbitrator Fredric Horowitz.
Coming back from hip surgery in January, Rodriguez played his first game of the season Monday night in the series opener at Chicago.