08/12/2011 12:43 EDT | Updated 10/11/2011 05:12 EDT

Djokovic reaches Rogers Cup quarter-finals, Federer latest casualty

MONTREAL - Some top players have shown signs of rust at the Rogers Cup, but not top-seeded Novak Djokovic.

The 24-year-old Serb kept his strong season alive with a 7-5, 6-3 victory over Marin Celic of Croatia on Thursday to reach the quarter-finals of the US$2.43 million Masters Series event. He's the last of the top four seeds still alive in the tournament after No. 3 Roger Federer was upset by 13th seed Jo-Wilfried Tsonga 7-6 (3), 4-6, 6-1.

In his second match since taking over the No. 1 ranking with a victory at Wimbledon four weeks ago, Djokovic broke the lanky Cilic's heavy serve twice in the second set to improve to 50-1 this year — including 26-0 on hard courts.

He had beaten another former top-10 player, Evgeny Davydenko, in straight sets in the second round.

''Both of the matches I've played here were against good players, but I didn't get any rhythm in either match,'' he lamented. ''Conditions were quite different today.

''There was a lot of wind. It wasn't a beautiful match to play or watch, but I guess in the right moments I kept the ball in the court to make my opponent make unforced errors. I was just more patient and played well, so I guess that's the positive.''

The tournament had already lost defending champion Andy Murray and second-seeded Rafael Nadal to upsets in the early rounds before losing Swiss star Federer in third-round action.

Federer, the Rogers Cup runner-up to Murray last year, lost to Tsonga for the second time at this tournament. Tsonga beat Federer, then ranked No. 1 in the world, in the quarter-finals of the 2009 event. Tsonga also beat Federer at Wimbledon this year.

Tsonga dominated the third set with dominant serves and quick groundstrokes, and Federer found himself unable to match the Frenchman.

"(Tsonga) made amazing shots," Federer said. "I don't think I played bad, but I really didn't have a good start to the third set, which didn't help."

Tsonga will face Nicolas Almagro of Spain in the quarter-finals. Almagro came back after being broken in the first set to defeat 10th seed Richard Gasquet of France 7-6 (5), 6-3.

Ivan Dodig, the 41st-ranked Croat who beat Nadal, had little left a day later as he went down 6-1, 6-4 to unseeded Serb Janko Tipsarevic.

Tipsarevic will face seventh-seeded Tomas Berdych in the quarter-finals on Friday. He is 2-0 in his career against the Czech veteran. Berdych downed Ivo Karlovic 6-3, 7-6 (2).

Stanislas Wawrinka ousted Kevin Anderson 6-4, 4-6, 6-4 and Mardy Fish beat Ernests Gulbis 4-6, 6-3, 6-4.

In doubles, Daniel Nestor of Toronto and Max Mirnyi of Belarus downed Sergiy Stakhovsky of Ukraine and Mikhail Youzhny of Russia 6-4, 6-4 to reach the quarter-finals.

Djokovic, who is seeking a ninth tournament win this year, said it is normal for top players to be a little off their games after the break most of them take between grass court play at Wimbledon and the hard court season leading up to the U.S. Open.

Upsets have also befallen top players at the women's Rogers Cup in Toronto, where Maria Sharapova was the latest star to go down on Thursday.

''I can't talk for all players, but the fact is that for most of the top players who don't play for a few weeks it's normal to expect that the opening matches of the tournament will be tricky,'' said Djokovic. ''You're still trying to find the rhythm, trying to get used to the conditions and getting into tournament mode.

''But it's normal to have those (breaks) in a year. You have to have them. We had seven months of consistent competition, week after week. The schedule is so demanding that even these couple of weeks off is like a dream come true. Each year, most of the top players don't play anything between Wimbledon and (the Rogers Cup).''

Djokovic's next opponent will be fifth-seeded Frenchman Gael Monfils, who downed 12th-seeded Viktor Troicki of Serbia 3-6, 7-6 (0), 7-6 (5).

The six-foot-five Berdych evened his career mark against the six-foot-10 Karlovic at 2-2, but it was their first meeting in three years.

"It's totally different than three years ago and I'm sure it's the same for him," Berdych said. "Today I was more focused and patient. I got a chance in the first set and made it and the same in the second during the tiebreak.

"(Karlovic) and John Isner are the ones who really make bomb serves. That's his main weapon and then he likes to come to the net where he plays well because he's tall."

It is the second year in a row and the third time overall that Berdych has reached the Rogers Cup quarters. He has never made the semifinals.

His path may be easier now that Nadal is out of his section of the drawsheet and he will face the 24th-ranked Tipsarevic instead.