The Wimbledon champion wrapped up a routine 6-3 6-2 6-2 win to book his place in the last 16 at Flushing Meadows, reaching the fourth round for the 22nd consecutive time at a Grand Slam.
“So far, so good,” said Djokovic. “The performances in all three rounds are no less than I wanted, expected and hoped that I could play.
“Sam is a big server and has a very powerful game. I had to move him around the court – he’s a big guy, doesn’t move so well.
“Of course as the tournament progresses the opponents will be tougher, but I am ready.”
Djokovic will face either Germany’s Philipp Kohlschreiber or American John Isner for a place in the quarter-finals.
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