Novak Djokovic advanced to the semi-finals of the US Open for the second year running after defeating Andy Roddick 6-2 6-3 3-6 7-6(5) under lights in front of 23,000 frenzied Americans who were desperate to see a final set that never came.

The American no.1, seeded 8, looked certain to take the match into a fifth set when he led 5-4 and 30-0 on serve in the fourth set, but then squandered his advantage by virtue of two consecutive double faults and a beautiful two-handed backhand lob winner from his opponent.

The contest didn't really get going until midway through the third set with the Serb having pocketed the opening two sets at a canter in barely an hour as he dominated proceedings off the ground with Roddick searching desperately for some inspiration and consistency.

It finally arrived courtesy of a wretched error strewn Djokovic service game which handed the grateful American a 3-1 lead in the third set. The former world no.1 used this as a springboard to launch his comeback as the New York crowd hollered for their man to fight his way back.

In next to no time Roddick riding a crest of a wave, served out the set to love with a huge ace up the centre and then broke the disgruntled world no.3 in the seventh game of the fourth set. He set up break point with a sensational backhand winner that beat the scampering Serb on his baseline for a clean winner, and then converted by nailing another two-hander down the line to raucous applause from the partisan crowd.

Just when Roddick looked to be in cruise control when serving for the set at 5-4, the wheels unexpectedly came off and the relieved Serb won a closely contested breaker 7-5 when a Roddick forehand return sailed long.

Both men served 15 aces, but Djokovic was superior in his break point conversion of 100% (5/5) whereas Roddick could only manage 30% (3/10).

"It was very close; I mean, he was serving 5‑4 and 30‑Love, and plus staying on the better side on the court, so I really didn't think I would get myself out of that position, but, you know, obviously I played well", Djokovic said. "I lost that third set, and I was a break down. He was serving, and he was just getting into the rhythm of the serve. He was serving huge. And then suddenly he makes two double faults, so I used my opportunity."

Djokovic will go into his semi-final match against defending champion Roger Federer, a 7-6(5) 6-4 7-6(5) winner over Luxembourg qualifier Gilles Muller, knowing that should he win and go on to take the title, he will overtake the Swiss as world no.2.

"It's a bit strange, though, to see No. 2 next to his name, you know. He was so dominant in last couple of years, and I lost to him here the finals last year. I took some, well, necessary thoughts, and things out of that match, so I can improve in the next challenges or next encounters, and I won against him this year in Australian Open. That was my best tournament of the career, and against him, that was one of my best matches. Hopefully I can do the same. I just need to be myself and need to be aggressive."

Roddick was not unduly concerned about the double faults that cost him the fourth set, feeling that he had to go for bigger second serves.

"I doubled twice, but you know what? I honestly don't feel like they were super‑tight doubles, and I've been going for bigger second serves kind of the whole way back because he was jumping on my second serve early", Roddick explained. "Just missed them. He had a really good shot on break point. I've been playing pretty high‑risk, high‑reward tennis and I probably wasn't about to stop. Given the choice again, I'd probably go for them, you know. That's what got me back in the match."

Coming back from a two sets deficit against the world no.3 playing on his favourite surface was asking a little too much of the American who must be happy to have found some form after a poor hardcourt season which saw him skip the Olympics in order to prepare for the final Slam of the year.

"There's not a whole lot of regret in the way I played the last two sets. The first two is another story. Like I said, I dug myself a hole that was real tough to get out of. I gave it my best shot to get out them but I think it was too little too late.

"I just wasn't seeing the ball; I felt like everything was a little bit rushed, and it was unfortunate. By the time I got my legs under me he was on a little bit of a roll. The fourth set I hit the ball as well as I have this whole tournament. Credit to him on the tiebreaker, he really beared down on a couple of points where I really hit the ball well to win it. He's great at winning those tough matches, and I'm disappointed that I spotted him a set before I actually got my feet under me, but, you know, I'm happy with the effort I made to try to come back."

Andre Jones

Flushing Meadows

New York