Tennis US Open ChampionshipsThe chances of Andy Roddick beating Roger Federer seem altogether more remote as time goes by. They have met 14 times, with the American winning just once, and even the most patriotic of US tennis commentators would be hard pushed to make a case for the A-Rod beating the world number one again in their quarter-final here at Flushing Meadows.

"I'd love to see him bust through here and take one of those titles away from Federer," said James Blake, who was beaten over five sets by Tommy Haas in the fourth round, leaving Roddick isolated and adrift as the only American left in the last eight of the men's singles.

"I love the way Andy is playing, love the way he's competing. (He is) just serving huge, as always."

So he is, and so was the 6ft 9in US rookie John Isner whom Federer unpicked with surgical precision in the third round. If there is a smidgen of encouragement for Roddick it is that against both Isner and Spain's Feliciano Lopez in the fourth round the Swiss lost the opening set, something he has not done in consecutive matches in any slam since the 2002 US Open.

Roddick needs to get in Federer's face from the opening minutes. Working under the guidance of Jimmy Connors, five times a US Open champion, the American gave a much-improved performance in last year's final, and then had three match points against Federer during the end-of-season Tennis Masters Cup in Shanghai.

He believed he was closing the gap, only to be blown away 6-4, 6-0, 6-2 in the semi-finals of this year's Australian Open.

Roddick remains damaged goods in American eyes, a one-slam wonder whose title here in 2003 is deemed by most to be his last. He saved himself some energy in the fourth round when Tomas Berdych pulled out in the second set with breathing difficulties.

"I don't know if it will help being fresh against Roger. All I know is that it's better than being dead tired," said Roddick.

"I'm excited, and the crowd will be electric. I expect a lot of myself, although I don't really think anybody else does."

Meanwhile Juan Ignacio Chela outlasted Stanislas Wawrinka in an erratic match to reach the last eight.

The Argentinian 20th seed defeated his Swiss opponent 4-6, 6-2, 7-6, 1-6, 6-4 in three hours 41 minutes at Louis Armstrong Stadium and now awaits the winner of the all-Spanish fourth round meeting between second seed Rafael Nadal and number 15 David Ferrer.

Both Chela and Wawrinka had reached the last 16 courtesy of five-set victories and the fatigue from those encounters quickly told as both committed a string of unforced errors.

Wawrinka, who had previously beaten Chela twice, had been in a commanding position to advance at 2-0 up in the fifth. Yet it was Chela, 29, who prevailed; his greater experience and determination seeing him through.

Chela started in lethargic mood and lost the first set 6-4 but bounced back in the second set 6-2. In the third set, both players looked poor, with two breaks of serve each until Wawrinka at last found some consistency to twice hold at 5-4. Unfortunately for him, the rest of his game then collapsed as he surrendered meekly to the Chela serve and the set went to a tiebreak, which the South American took to move into a 2-1 lead.

Wawrinka took the fourth 6-1 but in a see-saw last set let his rival back into the match and Chela broke again for a 4-3 lead before going on to triumph 6-4.

Flushing Meadows Results

WOMEN'S SINGLES: Fourth round: (4) Svetlana Kuznetsova (Rus) bt Victoria Azarenka (Blr) 6-2 6-3, Agnes Szavay (Hun) bt Julia Vakulenko (Ukr) 6-4 7-6 (7-1), (18) Shahar Peer (Isr) bt (30) Agnieska Radwanska (Pol) 6-4 6-1, (6) Anna Chakvetadze (Rus) bt Tamira Paszek (Aut) 6-1 7-5,

MEN'S SINGLES: Fourth round: (5) Andy Roddick (USA) bt (9) Tomas Berdych (Cze) 7-6 (8-6) 2-0 ret, (10) Tommy Haas (Ger) bt (6) James Blake (USA) 4-6 6-4 3-6 6-0 7-6 (7-4), (4) Nikolay Davydenko (Rus) bt Hyung Taik Lee (Kor) 6-1 6-3 6-4, (1) Roger Federer (Swi) bt Feliciano Lopez (Spa) 3-6 6-4 6-1 6-4, (17) Carlos Moya (Spa) bt Ernest Gulbis (Lat) 7-5 6-2 6-7 (5-7) 6-4, (20) Juan Ignacio Chela (Arg) bt Stanislas Wawrinka (Sui) 4-6 6-2 7-6 (8-6) 1-6 6-4, (17) Carlos Moya (Spa) bt Ernest Gulbis (Lat) 7-5 6-2 6-7 (5-7) 6-4.

WOMEN'S DOUBLES: Quarter-final: (14) Agnes Szavay (Hun) and Vladimira Uhlirova (Cze) bt Stephanie Foretz (Fra) and Yaroslava Shvedova (Rus) 3-6 6-3 6-3.

MEN'S DOUBLES: Quarter-final: (5) Paul Hanley (Aus) and Kevin Ullyett (Zim) bt Marcelo Melo (Bra) and Andre Sa (Bra) 7-5 6-3.