Isner shows Roddick the door

Andy Roddick, left, lost to John Isner, a player he has mentored in the past. Timothy Clary / AFP

NEW YORK // Flushing Meadows shook with an explosion of deafening roars on Saturday, a day of upsets, as American sensations John Isner and Melanie Oudin sent former champions Andy Roddick and Maria Sharapova spinning out of the US Open. It was a bad day for Russia with Dinara Safina's luck and patience finally running out as she followed Sharapova out of the tournament. The world No 1 was beaten 6-4 2-6 7-6 (7-5) by Czech teenager Petra Kvitova.

Isner and Oudin both showed their "bulldog" spirit to full effect. While 55th-ranked Isner was delighted to pull off the biggest shock of the men's draw, Oudin followed up her win over world No 4 Elena Dementieva by thumping another Russian. The big-serving Roddick met his match when he came face to face with the tall (6ft 9in) Isner, he had mentored up the ranks. As a way of thanks Isner boomed in 38 aces to trample the fifth seed 7-6, 6-3, 3-6, 5-7, 7-6.

"I'm happy for him. I'm mad that obviously it came at my expense," said Roddick. Roddick's loss only highlighted the lament by former greats Jimmy Connors and John McEnroe on Friday when the two came together for a few hits on an adjacent practice court. A legend himself, McEnroe said young Americans needed an inspiration like Connors. Connors, who used to coach Roddick, had added. "There needs to be a number of young Americans coming up at any one given time, and we need someone out there who captures imaginations to get the message out."

Roddick, the only American in the top 20, failed to make the most of the opportunity offered at his home grand slam to follow up on his runner-up finish at Wimbledon. The 17-year-old Oudin had the honour of ringing the opening bell at the Nasdaq stock exchange earlier this week and her stock rose even higher when she carved out a heart-pounding 3-6, 6-4, 7-5 third-round win over 29th seed Sharapova.

As some 23,000 fans cheered inside Arthur Ashe Stadium, those who could not cram into centre court watched transfixed on a giant TV screen in the main plaza. When Oudin finally sealed the three-hour triumph by belting a forehand winner, spectators inside and outside the arena leapt to their feet to give her a standing ovation. Oudin simply looked dazed as she dropped her racket before raising her weary arms to acknowledge the cheers. "I just kept fighting as hard as I could. I can't believe it," the 70th-ranked Oudin gasped as she tried to blink back tears.

"I just had a blast playing there," added Oudin, who will take on another Russian, Nadia Petrova, in the last 16. Isner summed up Oudin's feat by saying: "She's so gutsy. She plays with her heart out there. We really kind of have the same attributes. We got a little 'bulldog' in us. We fight really well." As the women's field continued to be decimated - with no seed left in the top quarter - Isner finally burst the bubble in the men's draw as until his win over Roddick, it looked as if all 16 top seeds could reach the fourth round of a grand slam for the first time.

Earlier, five-time champion Roger Federer and the world No 4 Novak Djokovic led a parade of seeds - Nikolay Davydenko (eight), Fernando Verdasco (10), Robin Soderling (12), Tommy Robredo (14) and Radek Stepanek (15) - into the second week of the major. Both Federer and Djokovic both suffered a hiccup though. The top seed Federer dropped the first set against Lleyton Hewitt before coming through. The Serbian Djokovic had to rub his eyes in disbelief as the American Jesse Witten - whose bulky frame suggests he would not look out of place on a rugby pitch - fought valiantly for almost three and half hours before succumbing 6-7, 6-3, 7-6, 6-4.

Witten is ranked 276th and had never won a tour match before this week. * With agencies