The tennis players’ association that was co-founded by Novak Djokovic has filed multiple lawsuits around the world against the sport’s tours and governing bodies.

Four-time Grand Slam champion Carlos Alcaraz says he was unaware there would be a class-action lawsuit filed in U.S. federal court against some of the groups that run tennis and made clear that he does not back the effort by the players’ association co-founded by Novak Djokovic.