TTMR
Hall of Fame
He didn't smack the ball at all. He simply emptied his pocket after the game was over, and sent the ball back without looking. OK, it was careless, but this was clearly not intentional, and the ball was not hit even too hard.
OK, I guess rules apply to everyone but this is simply a ridiculous way to end his US Open.
Djokovic has been playing pro/high level junior tennis for 20 years. He knows the rules.