Rabiot's mother and agent has been quoted as saying the midfielder is attempting to 'buy his freedom' from PSG, and the clubs still squabble over his contract status.
He was left out of the midweek game against Orleans, and there are reports that PSG are looking to sideline him indefinitely.
In a statement, Fifpro said Rabiot "has the right not to sign" a new deal.
"Is football about winning matches or making profits? Jean-Marc Bosman fought for this right and Fifpro defend it," the statement read.
Rabiot continues to be linked with a move to Barcelona as the dispute wages on, and could finally make the move next summer when his contract expires.