(CNN) -- Alex Rodriguez's fight against his 211-game suspension by Major League Baseball has officially begun.
The Major League Baseball Players Association on Wednesday filed a grievance on his behalf, appealing the suspension that MLB levied two days earlier after an investigation into the use of performance-enhancing drugs, association spokesman Greg Bouris said.
The New York Yankees third baseman can play while the suspension, which was to take effect Thursday, is appealed. He has been in the Yankees' lineup since returning from injury Monday, and went 1-for-5 at the plate Wednesday night in a 6-5 loss to the White Sox in Chicago.
MLB on Monday suspended Rodriguez and 12 other players, accusing them of having ties to the now-shuttered Biogenesis anti-aging clinic in South Florida and taking performance-enhancing drugs.
Rodriguez, 38, has denied the accusation. He received the longest suspension of the 13 players: 211 regular-season games, which would have seen him sit through the 2014 season.
The 12 other players accepted 50-game suspensions without pay.
Speaking to reporters Monday, Rodriguez declined to answer questions about whether he had used performance-enhancing drugs.
"I think we'll have a forum to discuss all of that, and we'll talk about it then," he said.
The league said Rodriguez's punishment is based on his alleged use and possession of banned performance-enhancing substances, including testosterone and human growth hormone, for multiple years.
Officials also accuse him of "engaging in a course of conduct intended to obstruct or frustrate" their investigation into the matter.
Rodriguez is considered one of the game's greatest sluggers. He has 647 home runs -- the fifth most ever -- in 19 seasons.
He holds the largest contract ever in American sports, signing with the Yankees in 2007 for $275 million over 10 years.
CNN's Jason Carroll and Catherine E. Shoichet contributed to this report.