NEW YORK — A year ago, U.S. Open fans fell for Novak Djokovic.

They loved his stylish play and, more so, his wit and his shtick.

They cheered raucously when Djokovic stuck around after winning his quarterfinal and, prompted by a TV interviewer, did spot-on impersonations of Maria Sharapova (pretending to tuck his hair behind his ears, exactly how the Russian does) and Rafael Nadal (even yanking at the back of his shorts, exactly how the Spaniard does).

My, how things were different after Djokovic won his 2008 U.S. Open quarterfinal.

Given an opportunity to address the Arthur Ashe Stadium crowd by the same TV interviewer after beating Andy Roddick in four sets Thursday night, Djokovic dispensed with niceties.

No charm this time.

Instead, the third-ranked Djokovic lashed out at the Roddick, taking him to task for making light of the Serb's series of medical issues earlier in the week.

"You know, Andy was saying I have 16 injuries in the last match," Djokovic said, anger in his voice. "Obviously, I don't, right?"

He was booed. Loudly.

And he wasn't deterred in the least.

"They're already against me because they think I'm faking everything, so it's all right," Djokovic said. "That's not nice, anyhow, to say in front of this crowd that I have 16 injuries and that I'm faking."

It will be fascinating to see how Djokovic is received when he faces four-time defending champion Roger Federer in the semifinals, which are scheduled for Saturday afternoon but could be moved if, as expected, Tropical Storm Hanna hits the area.

New No. 1 Rafael Nadal meets No. 6 Andy Murray in the other semifinal, but Federer-Djokovic will draw far more attention, and not just because it's a rematch of the 2007 final at Flushing Meadows.

Federer has drawn more support at this U.S. Open than at any other player, including the warmest reception during a parade of past champions on Day 1. Perhaps it's a result of his rougher-than-usual season, but he has suddenly become an adopted son at this site.

So Djokovic, who already was being harassed by a pro-Roddick home crowd during play, probably can expect to hear plenty from the stands.

He and Roddick both tried to smooth things over in their postmatch news conferences, although Roddick didn't completely let the Australian Open champion off the hook.

"I figure if you're going to joke and imitate other people and do the whole deal, then you should take it," Roddick said.

"Especially in Novak's case," Roddick said later, "if you're going to dish out all the stuff, then be able to take it with a smile."

During a lighthearted exhibition match in Arthur Ashe Stadium two days before the tournament began, they traded playful barbs. Djokovic imitated Roddick. Roddick imitated Djokovic. All in good fun.

The vibe was quite different Thursday. But after having a chance to think about what happened, Djokovic chalked it up to a misunderstanding.

He also felt it necessary, however, to defend his use of medical timeouts and requests for trainers. That's what started everything: During Djokovic's five-set victory over Tommy Robredo in the fourth round Tuesday, he asked for a trainer more than once to help him deal with a variety of ailments — ankle, hip, stomach and more.

"Did I trust him? No. No. I think he took his time, because ... he was a little bit more tired," Robredo said.

Roddick, who played his fourth-round match later that day, looked ahead to facing Djokovic and told the crowd, it sounded as though Djokovic had "about 16 injuries." Roddick later joked that perhaps Djokovic's issues also included SARS, bird flu, anthrax and a common cold.

This sort of thing has come up in the past with Djokovic.

He quit because of an infected blister on a toe while trailing Rafael Nadal in a 2007 Wimbledon semifinal. He also stopped after losing the first two sets of his 2006 French Open quarterfinal against Nadal, citing a back injury, and retired during his second-round match of the 2005 French Open.

At the Masters event at Monte Carlo, Monaco, in April, Djokovic quit while losing 6-3, 3-2 against Federer, then complained of dizziness and a sore throat.

Unprompted, Federer made a passing reference to that Thursday, saying, "We haven't played that much really. He gave up in Monaco."

In explaining why he addressed the issue and took on the fans Thursday night, the 21-year-old Djokovic sounded a weary note.

"Now, look, I had a very, very tough day yesterday. Physically I was feeling very exhausted and very empty," he said. "I wasn't able to practice. One of the reasons was physically that, you know, I was exhausted. And the other reason was that I just mentally had a lot of pressure."