Tennis ball or real thing?
The tennis ball is the big bulge.
I don't know why people think a tennis ball in the pocket is always the real thing? Not saying you think that but when you are a tennis player you know that almost all players at club level and a lot of pro's put the ball in the pocket and it's usually a tennis ball.
However, I will say djokovic when he is bulging is pretty hot. The Hi-Res of this photo you can see his stuff in the middle right on the seam of the shorts. HOT!!!! Thanks for the photo!