NEW YORK (AP) — Novak Djokovic put aside all of it, from his opponent's unheard-of, middle-of-a-set chance to change out of sweat-soaked clothes and shoes, to consecutive time violations because he let the serve clock expire, to the 16 break points he wasted.

All that mattered, really, was that Djokovic managed to do what Roger Federer could not two nights earlier: beat 55th-ranked John Millman at the U.S. Open.

Djokovic moved a step closer to a third championship at Flushing Meadows and 14th Grand Slam title overall by eliminating Millman 6-3, 6-4, 6-4 to get to the tournament's semifinals for an 11th appearance in a row. He sat out last year because of an injured right elbow.

The No. 6-seeded Djokovic, who won Wimbledon in July, had been drawn to face Federer in the quarterfinals. But Millman scuttled that showdown by stunning the 20-time Grand Slam champ in four sets in the fourth round on a hot and humid evening that Federer said sapped his energy and made it hard to breathe.

This night was cooler, as the temperature dipped into the 70s, but the humidity was above 80 percent, so with Millman drenched, he sought permission for a wardrobe change at 2-all in the second set. It was odd enough to see a player be allowed to do that during, instead of after, a set, but even odder for it to happen after an even number of games, rather than at an odd-game changeover.

"I was struggling. He was struggling. We were all sweating. Changing a lot of T-shirts, shorts," said Djokovic, who will face 2014 U.S. Open runner-up Kei Nishikori on Friday. "Just trying to find a way to hang in there."

When Millman apologized for leaving the court at that juncture, Djokovic replied, "I'm fine to have a little rest," then sat down on his sideline bench without a shirt on and cooled off.

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