In a match which finished past 0200 (0900 GMT), Argentine Nalbandian had four match points at 5-3 in the second set and another on his own serve at 5-4.

But Nadal showed amazing resilience to break back and then snatch the set on a tie-break, before ripping through the decider for his first win over Nalbandian in three attempts.

World number two Roger Federer, champion Novak Djokovic and fourth seed Andy Murray all joined Nadal in the last eight.

Nalbandian dominated Nadal for a set and a half and it was only when it reached match point that the Spaniard appeared to find his best form.

"I don't know (how I won)," Nadal said. "I had a lot of luck. I started the match with some doubt because the last two matches were very easy for him."

Once he broke the Nalbandian serve in the opening game of the third set, though, that was it and Nadal ran away with the rest of the set to set up a clash with another Argentine, Juan Martin Del Potro.

Federer was also made to battle for his quarter-final spot, beating Chilean Fernando Gonzalez 6-3 5-7 6-2.

"I enjoy playing (Gonzalez) because it's so tactical," Federer said.

"But then at the same time it's so brutal, so aggressive. You think you have a slight chance to win the point, and then you realise, no, there's actually none."

Federer cruised through the first set but Gonzalez, unleashing a series of spectacular forehand winners, broke in the 12th game of the second set to force a decider.

Federer then hit another gear, breaking in the third game of the third set and then again in the seventh before serving out for victory to set up a clash with Fernando Verdasco.

The Swiss has won both his previous matches with Verdasco, but the Spaniard looked in good form in beating Philipp Kohlschreiber of Germany 6-4 3-6 6-1.

"I'm looking forward to playing more baseline rallies against Verdasco," Federer said.

"I'm sure that's going to happen. It's a good thing that I'm still in the tournament and facing an opponent who actually is going to extend the rallies a little bit. It's going to be a nice match, I'm sure."

Third seed Djokovic saved a set point against another Swiss, Stanislas Wawrinka, in the second set before clinching a 7-6 7-6 victory, setting up a clash with seventh seed Andy Roddick, who beat Spaniard David Ferrer 7-6 3-6 6-3.

Djokovic beat Roddick at the US Open 2008 but did not endear himself to the crowd when he reacted to claims from the American that he had ‘faked’ a series of injuries.

The Serb then pulled out against Roddick when the two met at the Australian Open in January, citing heat exhaustion.

But Roddick said any problems they may have had were in the past.

"The thing that needs to be recognised is, regardless of our history, I think we've always respected each other's games, and we respect what the other has accomplished," he said.

"We talked about it. Are we best friends? Probably not, but I think we have a lot of respect for each other."

Fourth seed Murray cruised into the last eight when Tommy Robredo retired with a right wrist injury. The Scot was leading 6-2 3-0 when Robredo quit.