MONTREAL - Rafael Nadal's knees stood up just fine on an historic night at Uniprix Stadium.

The world No. 2 waltzed to a 6-3, 6-2 victory over mistake-prone Philipp Petzschner in third-round play at the US$3-million Rogers Cup on Thursday in the first real test of the tendinitis in both knees that kept him sidelined for the past 10 weeks.

Nadal's first match on Wednesday night was cut short when opponent David Ferrer retired midway through the first set with a sore knee.

"The movements were a little bit better, but I need more matches to get the rhythm," said Nadal, the tournament's defending champion. "I moved a bit better but sometimes my positioning wasn't perfect.

"I need to adjust the legs and feet more to play some shots. But I'm very happy because I'm in the quarter-finals, which is more than I expected when I came here. I have one match and a half right now and I expect to be ready for (Friday.)"

Nadal was among the eight top-ranked players in the world to reach the quarter-finals - the first time that has happened at an ATP tournament since rankings were introduced in 1973. The group, in order, has Roger Federer, Nadal, Andy Murray, Novak Djokovic, Andy Roddick, Juan Martin Del Porto, Jo-Wilfried Tsonga and Nikolay Davydenko.

"Certainly the top six have been putting up results very consistently this year," said Roddick. "This is probably one of the most consistent years I've had and I'm still looking at No. 5. There's a precedent being set by the top guys now."

Nadal shot off to a 3-0 lead in the first set and never looked back as the Spanish left-hander advanced to the quarter-finals, where he will face sixth-seeded Del Potro. The Argentine Del Potro, coming off a win last week in Washington, downed Victor Hanescu of Romania 3-6, 6-3, 6-4.

"I know I'm not the favourite for the match, but it gives me a chance to keep improving in my level," said Nadal. "He's playing well.

"He's No. 6 in the world. He won in Washington and he won a tough match (against Hanescu), so he's coming with big confidence. He has a good serve and good shots from the baseline. He's a very tough opponent for me right now."

The 23-year-old Nadal is in his first tournament since losing in the fourth round of the French Open on May 31.

After Ferrer withdrew Wednesday, Nadal's second match was a better test. Still, the Spaniard had little trouble with his German opponent, who did himself in with numerous unforced errors, particularly early in the first set, before a sellout crowd of 11,490 at centre court.

"He played very aggressive and had some good shots, but a lot of mistakes," added Nadal. "But my goal before the tournament was to keep improving and I think I am doing that.

"I love competition and I'll do my best to be ready. Even if I'm not at 100 per cent, I'm going to try my best to be competitive."

Nadal got a warm greeting as he entered in a royal blue shirt with striking yellow bands on his head and wrist to match the yellow slash on his shoes and racket.

Federer, in his first tournament since taking time off while his wife gave birth to twin girls, shook off some rust in a 6-3, 7-6 (5) win over Swiss compatriot Stanislas Wawrinka. Federer avenged a loss to 22nd-ranked Wawrinka on clay in Monte Carlo earlier this year.

Federer will next play Tsonga, a 6-3, 6-3 winner over his ninth-ranked French compatriot Gilles Simon.

Another quarter-final will see Roddick face Djokovic in a battle of strong hardcourt players.

Roddick fought off a strong service game from 10th-seeded Fernando Verdasco to defeat the Spanish southpaw 7-6 (2), 4-6, 7-6 (5). The American is 32-8 in tiebreakers this year.

Djokovic, the fourth seed, downed Mikhail Youzhny of Russia 6-3, 6-4. The Serb leads the ATP Tour with 49 match wins this year.

That sets up the sixth career meeting between Roddick and Djokovic. Roddick holds a 3-2 edge, including wins in their two meetings this year - at the Australian Open, where Djokovic retired in the fourth set from cramps and heat stress, and at Indian Wells.

"They were both on hardcourts, so hopefully I can get a chance to play better and win," said Djokovic. "We all know he's the biggest server in the game, next to Ivo Karlovic, and he's playing better since he started working with a new coach (Larry Stefanki).

"He's more aggressive. He played great in Wimbledon. He's on a roll, so it's going to be a difficult one."

Roddick had equal praise for Djokovic.

"We're very aware of what the other does well," said Roddick. "It goes without saying that I'll have to play well to advance.

"I don't think you can put much stock in a win that was six months ago. A lot has changed. And to his credit, he certainly didn't play that well that day."

Murray, of Britain, had little trouble dispatching former world No. 1 Juan Carlos Ferrero of Spain 6-1, 6-3 and Davydenko of Russia edged 11th-seeded Fernando Gonzalez of Chile 7-6 (2), 7-5.

Murray, who will face Davydenko in the quarter-finals, has a chance to overtake Nadal for the No. 2 world ranking if he goes far and the Spaniard falters.

Nadal said the ranking "doesn't matter. In the end, the important thing is to play well. The thing that makes me happy is to be competitive and win tournaments, no?"

Roddick improved to 9-2 in his career against Verdasco, but the two-hour 37-minute match in muggy conditions wasn't easy. The American got the edge when he broke service for 6-5 in the third set with a desperate cross-court shot at the end of a long exchange, and then winning the tiebreak when Verdasco hit two balls in a row long.

Verdasco broke back to force a tiebreaker, but Roddick prevailed as Verdasco hit match point long.

Roddick is playing his second tournament since his thrilling five-set loss to Federer in the Wimbledon final.

Djokovic's first meeting with Roddick was a win in the quarter-finals at the 2007 Rogers Cup in Montreal. Djokovic went on to defeat Nadal in the semifinals and Federer in the final to claim one of the first big victories of his career.

The same scenario is possible this year, as the draw has a potential semifinal meeting with Nadal and a potential meeting with Federer in the final.

"Most of us guys didn't play any events prior to Montreal (since Wimbledon in June)," said Djokovic. "But this is what you want prior to a grand slam (the U.S. Open that starts Aug. 31 in New York). You want to play the best players in the world to test yourself, to see where you are at the moment and see if you can win against them."

Already, the top 11 seeds had reached the round of 16 for the first time in the tournament's history since the Open era began in 1968. They included 14 players who either are currently or have in the past been ranked in the world's top 10.

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