The Major League Baseball Players Assn. has filed a grievance to halt the 26 clubs from continuing their practice of limiting themselves to 24-man rosters instead of 25, according to a published report.
The grievance was filed Tuesday, the New York Times reported in its Wednesday editions.
"It's now apparent to us that they've changed the rule," Donald Fehr, the players association's executive director, told the paper.
For the past several years, major league clubs have carried 25 players on their roster as allowed by a collective bargaining agreement. A provision in the agreement allows clubs to carry as few as 24 players.
This year, all clubs have agreed to restrict themselves to 24 players.
"What clubs have said is you can have 24 players and not more than 24," Fehr said. "It's clear that some clubs would go to 25 if others would, but no one wants to be the first. This costs players jobs and affects competition."