NEW YORK (AP) -- Still waiting for a test at this U.S. Open, top-seeded Novak Djokovic moved into the fourth round by beating 95th-ranked Joao Sousa of Portugal 6-0, 6-2, 6-2 on Sunday night.
Djokovic's serve was broken only once, when he served for the match at 5-1 in the third set. He's been broken once in each match while winning all nine sets he's played so far.
His six career Grand Slam titles include the 2011 U.S. Open, and he has reached at least the semifinals at Flushing Meadows each of the past six years. Djokovic lost in last year's final to Andy Murray.
Djokovic put together a 34-10 edge in winners against Sousa, who was trying to become the first man from Portugal to reach the fourth round at any Grand Slam tournament.
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