Novak Djokovic wins 2015 US Open

Novak Djokovic of Serbia with the US Open Trophy after beating Roger Federer of Switzerland in the men's singles final at USTA Billie Jean King National Tennis Center. (AFP)

Novak Djokovic of Serbia (right) shakes hands with Roger Federer of Switzerland after beating him in the men's championship match of the US Open tennis tournament. (AP Photo)

Novak Djokovic of Serbia kisses the US Open Trophy after beating Roger Federer of Switzerland in the men's singles final. (AFP)

Roger Federer, of Switzerland, returns a shot to Novak Djokovic, of Serbia, during the men's championship match. (AP Photo)

Mirka Federer, Roger Federer's wife, watches play between Federer and Novak Djokovic, of Serbia, during the men's championship match. (AP Photo)

Novak Djokovic, of Serbia, reacts after defeating Roger Federer, of Switzerland, in the men's championship match. (AP Photo)

Novak Djokovic, of Serbia, is thronged by supporters after beating Roger Federer, of Switzerland, in the men's championship match. (AP Photo)

Rain water streaks across practice courts before the men's championship match. (AP Photo)

Roger Federer, of Switzerland, reacts after winning the second set against Novak Djokovic, of Serbia, during the men's championship match. (AP Photo)

Novak Djokovic, of Serbia, falls to the court while trying to return a shot to Roger Federer. (AP Photo)

Roger Federer, of Switzerland, serves to Novak Djokovic, of Serbia, during the men's championship match of the U.S. Open tennis tournament. (AP Photo)

Novak Djokovic, of Serbia, reacts after winning a game against Roger Federer, of Switzerland, in the men's championship match. (AP Photo)