Against Roger, you can't really play the style of tennis that you want to play out there. That's the hard thing.'

Djokovic came through a match containing 15 breaks of serve, taking nearly three and a half hours to advance into the second week over journeyman Witten, who returns to the Challenger circuit next week in Oklahoma after his brush with glory.

'Those (tough) matches have to appear sometime during the tournament,' said Djokovic. 'Maybe the good thing is that I have played this match in the third round. I have high ambitions for this tournament.'

Russian eighth seed Nikolay Davydenko put out Federer's good friend Marco Chiudinelli 6-4, 7-5, 7-5 while Spain's tenth seed Fernando Verdasco stopped German Tommy Haas 3-6, 7-5, 7-6 (10-8), 1-6, 6-4.

French Open finalist Robin Soderling, seeded 12th, beat American Sam Querrey 6-2, 7-5, 6-7 (6-8), 6-1.

In women's play, Nadia Petrova will face off in the fourth round against American surprise packet Melanie Oudin, who stunned 2006 champion Maria Sharapova 3-6, 6-4, 7-5.

The Russian three-time Grand Slam winner took treatment on her upper arm in the third set and was plagued by a demoralising 21 double-faults.

Oudin, 17, has duplicated her Wimbledon round of 16 showings and was in complete shock after adding the Russian to a hit list that began with fourth seed Elena Dementieva.

'I fought as hard as I could, I just can't believe this. I've always been so competitive. I really have belief. I got lucky in the third set as Maria double-faulted. But I was putting pressure on her second serve.'

There were wins into the fourth round for sixth seed and 2004 winner Svetlana Kuznetsova, who defeated Shahar Peer 7-5, 6-1 and Caroline Wozniacki, the number nine Dane who put out Romania's Sorana Cirstea 6-3, 6-2.