The Major League Baseball Players Association will back Alex Rodriguez if the New York Yankees attempt to deny him any future payments.

"The union would challenge any breach of contract with the union," a source close to the MLBPA said. "A player can't be punished again for something he's already been punished for."

Under the terms of the contract Rodriguez signed in 2009, the Yankees would owe him a $6 million bonus if he hits six more homers and ties Willie Mays on the all-time home run list.

However, the Yankees are bracing for a battle, believing that mark is now tarnished and they won’t be able to use it for marketing purposes.