Novak Djokovic's created the PTPA believing it necessary for modern tennis as he was unhappy with some of the aspects of the ATP.
Martina Navratilova is one of the greatest tennis players of all time and she was never one to shy away from speaking her mind about topics she finds important. Her career has always been like this and in a recent interview she criticised Djokovic for his PTPA initiative believing it unhelpful for tennis.
"He is convinced he did the right thing. I disagree with Nole on this, but he is free to do as he wants. I believe that this initiative did not help tennis I think she should take a step back and put his energy into something that really helps our sport."
She is hardly the same in that regard as both Roger Federer and Rafael Nadal were not receptive to the idea of calling for unity in the sport under the banner of the ATP. Some players were more respective to the idea of a dedicated player's union that would work together with the Tour. Andy Roddick was very outspoken for the need to have something like that as early as 2011.
Andy Murray was lukewarm on it albeit he did not totally reject it while Milos Raonic and Diego Schwartzman supported it. Other notable supporters include John Isner, Reilly Opelka, Hubert Hurkacz, Pablo Carreno Busta, Denis Shapovalov and former pros such as Patrick McEnroe and John Isner.