The PTPA, an advocacy group established by Novak Djokovic and Vasek Pospisil in 2019 and supported by Australia's Nick Kyrgios, filed a lawsuit on Tuesday accusing the ATP, WTA, International Tennis Federation and International Tennis Integrity Agency of anti-competitive practices.
It said the governing bodies were also disregarding player welfare, and in one section of the 163-page document included a quote from four-time grand slam champion Alcaraz, who had criticised the hectic tennis calendar last September.
"It was surprising for me, because no one had told me about it," Alcaraz told reporters at the Miami Open.
"Yesterday I saw on social media that they put something I said in a press conference in the documents and I wasn't aware of it. I honestly don't support that letter, because I wasn't aware of it."
Men's governing body the ATP rejected the PTPA's claims and said the advocacy group was guilty of "division and distraction", while the women's WTA described the lawsuit as "regrettable and misguided".
Pospisil said the PTPA had spoken to more than 300 players and had plenty of support, including from top players.
Kyrgios, one of the 12 current and former players named as plaintiffs along with the PTPA in the US suit in New York, said it marked a "special moment" and it was high time the players' voices were heard.
"There are things I agree with and there are other things I don't agree with," Alcaraz added.
"Anyway, the main thing is I don't support what was done."Â
