Venue: Flushing Meadows, New York Date: 31 August - 13 September
BBC coverage: Live text commentaries on the website from 1600 BST each day, regular updates on 5 live, full commentary on 5 live sports extra in week two, both finals on 5 live
Federer will face either James Blake or Tommy Robredo in the last 16
Defending champion Roger Federer moved into round four of the US Open with victory over Lleyton Hewitt but Andy Roddick was knocked out by John Isner.
Top seed Federer came from behind to beat Hewitt 4-6 6-3 7-5 6-4 and will next play 14th seed Tommy Robredo.
But Roddick, seeded fifth, was stunned 7-6 (7-3) 6-3 3-6 5-7 7-6 (7-5) by unseeded fellow American Isner in a thriller lasting just over four hours.
Fourth seed Novak Djokovic battled to a four-set win against Jesse Witten.
Fernando Verdasco hit back from a break down in the final set to edge out German veteran Tommy Haas 3-6 7-5 7-6 (10-8) 1-6 6-4 and he will now play Isner.
Russia's Nikolay Davydenko, who is still yet to drop a set in the tournament, was made to work for his 6-4 7-5 7-5 win over world number 161 Marco Chiudinelli.
The eighth seed will face Robin Soderling in the fourth round after the Swede saw off American Sam Querrey 6-2 7-5 6-7 (6-8) 6-1.
Federer, the world number one, struggled to find a way past a scampering Hewitt in the early stages of the match and saw his break in the sixth game immediately wiped out by one from the Australian.
After facing down two break points in his next service game, Federer surrendered on a third to hand the first set to his 28-year-old opponent.
But Federer suddenly found his range to break Hewitt to love in the fourth game of the second set before holding his serve in similarly emphatic fashion to compound his advantage.
The pair were finally separated in a tight third set as Hewitt, who had lost the pair's previous 13 meetings, sent a slice long to allow Federer to edge ahead for the first time.
Hewitt fought bravely in the final set as he broke back at 5-2 down, but he could only delay his demise.
Federer, who committed 59 unforced errors in victory, admitted that he could easily have missed out on a a place in the last 16.
"It could have gone either way," he said. "He had a good start and he believed maybe more today than in some of the other ones he played against me.
"The way I came through, I was very happy, because I knew that being down a set against Lleyton is always going to be a difficult situation for me to be in.
"Make one more mistake and I'm in the fifth set maybe, or I go down completely. So I was relieved coming through."
Federer will next face Spaniard Robredo who beat American fans' favourite James Blake in straight sets 7-6 (7-2) 6-4 6-4.
Roddick became the first big-name seed to crash out of the tournament as he succumbed to Isner.
Isner hit a staggering 38 aces to Roddick's 20
The 2003 champion came into Flushing Meadows off the back of his appearance in the Wimbledon final but Isner proved he was no respecter of major tournament form.
The opening set stayed with serve as Isner sent down nine aces and Roddick four to force a tie-break, which the world number 55 took with some powerhouse tennis.
Roddick looked increasingly tetchy as Isner continued to play out of his skin, breaking the fifth seed to take a 4-2 lead and serving out at 5-3 with an ace.
The 6ft 9in right-hander had more than just a booming serve, though, and to Roddick's frustration he was more than happy to come to the net and attempt to lob his opponent.
Roddick, however, was edging into the ascendancy in the third set and he made the breakthrough in game eight before serving out the set to love.
The fourth set was equally tight but Isner almost wrapped up proceedings when, as he served to stay in the match, Roddick double faulted at 15-30 to give his opponent match point.
It was saved with an ace and Roddick recovered to break Isner's serve at 5-5 and serve out the set with an ace.
There was little to chose between the players in the decider and the quality remaining high until the very end.
In the tie-break, Isner claimed earned a mini-break with a cross-court backhand to move 4-2 ahead and soon had three match points.
I was able to make the quarter-finals last year and I was playing terrible and didn't make it past the third round this year - that's just the way it is sometimes
Roddick saved the first two with aces, but then netted a forehand to hand Isner the biggest win of his career to date.
"I played well and I think I deserve it," said the 24-year-old, who ho had lost his only other five-set match in the first round of the 2008 French Open.
"I just played well, stuck to the game plan and never panicked. Even though I only broke serve once, I thought I made him play a lot of balls.
"Maybe I was just fortunate. Maybe I caught him on an off day."
Roddick had no complaints about his defeat and suggested Isner found his best form when it really mattered.
"Bottom line is he played great in the breakers. He rolled the dice, came in. I made him play his last four volleys. He played well when he had to.
"It's tough. I don't know if I've come to a tournament, a Slam, with as much confidence as I did with this tournament and leaving earlier than I want to.
"The fact that I was able to make the quarter-finals last year and I was playing just terrible, and didn't make it past the third round this year, that's just the way it is sometimes.
"That's the thing with sports - there's not always a good reason for it."
Witten's $48,000 cheque is more than double his entire earnings for 2009
Djokovic, who had not dropped a set in his first two matches, struggled in the heat before eventually sealing a 6-7 (2-7) 6-3 7-6 (7-2) 6-4 win over American qualifier Witten.
The gap of 272 ranking places between the two was hard to detect as Witten, who had beaten 29th seed Igor Andreev in the first round, took the first set on a tie-break.
Djokovic may have expected to cruise to victory after levelling in the second but, backed by a partisan crowd, Witten battled on to keep the Serb on court for almost three and a half hours.
"Looking at that match, I don't know who was number four in the world," said Djokovic said. "It was a tough win. For either one it would have been well deserved."
Witten, 26, who had not won a tour-level match before the event, is expected to rise around 100 places in the next set of rankings on the back of his performances.
"It gives me some money to keep playing. So now I can afford to keep playing for the rest of the year, at least," he said.
"I don't know how good I am, so it's good to kind of see that I can play with these guys and I kind of belong a little bit here."
Standing between Djokovic and a place in the quarter-finals is 15th seed Radek Stepanek, who also made heavy weather of his third-round match before eventually overcoming Philipp Kohlschreiber 4-6 6-2 6-3 6-3.