LOL I love how people are shocked that tennis players have low BF. There is no sport on earth you can play for 5-6 hours straight then a couple days later you have to do it all over again. Even marathon runners get a longer break. Tennis is one of the most grueling sports ever considering you want to be strong but have to manage the long cardio sessions and crazy schedule. To work out and maintain muscle mass thought a catabolic state and play through injuries etc.
And Federer chubby? LMAO the guy is one of the most fit players on tour. He goes through multiple practice partners while training in Dubai in crazy hot conditions for many hours every day. The guy is a race horse.