Charles Krupa, Associated Press
Andy Roddick reacts during his loss to Novak Djokovic at the U.S. Open.

NEW YORK — Novak Djokovic heard what Andy Roddick said about him and didn't like it one bit.

Still, as much motivation as Djokovic might have derived from that, and as well as he played in their U.S. Open quarterfinal Thursday night, Roddick's own uncharacteristic serving miscues had a lot to do with the 2003 champion's 6-2, 6-3, 3-6, 7-6 (5) loss.

After working his way back from a huge deficit, Roddick was two points from forcing a fifth set at 5-4, 30-love in the fourth. But he double-faulted twice in a row and was broken for the fifth time — twice more than he lost on serve in his first four matches combined.

"You know what? I honestly don't feel like they were super-tight doubles," Roddick said. "I had been playing pretty high-risk, high-reward tennis to get back and I probably wasn't about to stop."

But the first question Roddick was asked had to do with his verbal squabble with Djokovic, who took offense at comments the American made about how ill and injured the Serb was after the previous round.

"It was completely meant in jest," Roddick said. "I should know better. But listen, I joke all the time. I don't think anyone in their right mind takes me serious."

In Djokovic's prior match, a five-set ordeal Tuesday against No. 15 Tommy Robredo, the reigning Australian Open champion called for the trainer more than once as he dealt with hip, ankle, stomach and breathing issues.

Asked then about Djokovic's problems, Roddick kidded around, checking whether the list shouldn't also include bird flu, anthrax, SARS and a common cold and said: "He's either quick to call a trainer or he's the most courageous guy of all time."

What seemed to rile Djokovic the most were what Roddick said in an on-court interview that day: "I've got to feel good. He's got about 16 injuries right now."

After beating Roddick, ending the match with a 125 mph serve that drew a long return, Djokovic made reference to those words.

"That's not nice anyhow to say in front of this crowd that I have 16 injuries and that I'm faking," Djokovic said during a postmatch interview that drew boos from the spectators in Arthur Ashe Stadium.

The third-seeded Djokovic advanced to a semifinal meeting against Roger Federer.

The other men's semifinal is No. 1 Rafael Nadal vs. No. 6 Andy Murray.

The men's semifinals and women's final are all scheduled for Saturday, but tournament organizers have seen forecasts calling for about 12 hours of rain and wind at up to 35 mph that day. So they began the process of negotiating with TV networks and preparing contingency plans, including weighing the possibility of announcing Friday that no tennis would be played Saturday, and that the men's final would be shifted from Sunday to Monday.

In the women's semifinals today, two-time champion Serena Williams faces Dinara Safina, and Jelena Jankovic meets Elena Dementieva. One of the four will move up to No. 1 in the rankings after the tournament.

Federer spent a record 237 consecutive weeks atop the rankings from February 2004 until last month, when Nadal supplanted him. That's only one of several streaks Federer has seen snapped in 2008.

He reached a record 10 consecutive major finals, until losing to Djokovic in the Australian Open semifinals in January. He won a record-tying five consecutive Wimbledon titles, until losing a 9-7 fifth set to Nadal in near-darkness in July. He was seeded No. 1 at 18 consecutive Grand Slam tournaments, until Nadal relegated him to No. 2 at this one.

"There's a lot at stake for him, obviously, as far as, you know, not having won a major this year and losing a No. 1 ranking. So he seems to be obviously very focused and is playing better," said Patrick McEnroe, the U.S. Davis Cup captain who also is coaching Roddick.

"I don't think he's playing quite at the level that he was in the last couple years," McEnroe added, "but he's certainly capable of turning it around."

On Thursday, as the break points and the set points slipped away, as his shouts of self-admonishment grew louder, it was hard to imagine Federer was having this tough a time in his quarterfinal against a man ranked 130th.

A man who arrived at Flushing Meadows with a 3-4 tour record this year.

A man who was kicked out of his hotel because it didn't occur to him to book a room long enough to stay past the third round of a Grand Slam tournament for the first time.

Fans used to watch Federer hoping to be awed by his brilliance. Now they wonder: Is he going to hang on? For the most part, even during this poor-by-his-standards season, he does get by. Federer did just that against Muller.

"He created a monster, like he said a couple years ago. He won everything. And now everybody expects him to win everything, and, I mean, he's also just human," Muller said. "Even today ... you could still see why he was No. 1 — and still No. 2 now. Every time the score was tied, he came up with a better shot."