I have not seen this documentary, but Novak Djokovic is a vegan and an executive producer for The Game Changers (trailer and interviews below).  Novak Djokovic and Venus Williams both eat plant-based diets so this may be something that is picked up by other tennis players.

As a matter of full disclosure, I have been a vegetarian since November 2011.  I am not a vegan and would not describe myself as any sort of dietary expert.  I have tried veganism at times and generally enjoyed benefits from it, but I have also found it to be a difficult standard to meet with a job and children.  I will review the documentary when I get the chance.