World number three Carlos Alcaraz said he does not support the legal action being taken against tennis' governing bodies by the players' union co-founded by Novak Djokovic.
The Professional Tennis Players' Association (PTPA) filed papers on Tuesday criticising the schedule, ranking systems and control over image rights.
The lawsuit seeks an end to what it describes as "monopolistic control" of the tennis tour, as well as financial compensation from the ATP, the WTA, the International Tennis Federation (ITF) and the International Tennis Integrity Agency (ITIA).
"It was surprising for me, because no one had told me about it," Alcaraz, 21, told reporters at the Miami Open.