A quick glance towards the Centre Court scoreboard at the Olympic Tennis Centre hardly helped Roger Federer's [Images] prickly demeanour on Tuesday.

As the Swiss went through a sweaty two-hour practice with doubles partner Stanislas Wawrinka the name of Tomas Berdych was frozen on to the screen alongside that of Federer.

A reminder of the Czech who stunned him at the Olympics [Images] four years ago in Athens was either a pure coincidence or the work of some mischievous technician. Whatever, Federer was not laughing as he avoided waiting reporters.

He barely smiled and hardly looked in the mood for a party at the world's greatest sporting festival as he went through his routines in sweltering conditions searching for the form that has suddenly deserted him.

Even his long-term girlfriend Mirka Vavrinec got the silent treatment as she sat on a courtside chair handing out water to the 12-times grand slam champion who lost his Wimbledon [Images] crown to Rafael Nadal [Images] last month and is soon to hand over the world number one ranking.

Over on an outside court the mood could hardly have been more different as Nadal, who will become top dog on August 18, enjoyed a relaxed hour-long hit with compatriot Tommy Robredo.

Nadal looked worry-free and jovial, chatting to reporters and signing autographs for some of the army of eager volunteers working at the venue.

He even played some football with a tennis ball with Robredo who he is sharing a room with in the nearby Olympic Village. He is clearly revelling in the atmosphere.

"It's something a little different to what we are used to but it's good," he told reporters. "Now that I'm going to be number one my only thoughts are on the Olympics."

The one worry for Nadal is the amount of mileage his legs have put in over the past two months, a run that earned him a fourth French Open title, his first Wimbledon title and also the Toronto Masters Series.

"I only got here yesterday and I'm jet-lagged. I'm more tired than normal. Physically I've had a lot of matches this summer but in three or four days I will feel different."

Nadal's 32-match unbeaten streak came to an end against Novak Djokovic [Images] in Cincinnati last week but he can be forgiven one bad day at the office.

Federer's recent form suggests something much more worrying. After his Wimbledon heartache he then lost in the first round at Toronto and last week in Cincinnati to Croatian Ivo Karlovic.

He has won only two minor titles all year but Wawrinka, who will also have high hopes of a medal here, says he believes Federer can answer those ready to predict a long-term slide.

"For me he is the best player ever," world number 10 Wawrinka told reporters. "He is in good spirits and will do what he needs to get back to world number one.

"He is going to be ready, it's one of his favourite tournaments for the year."

Wawrinka said he had chosen to stay in the athletes village, unlike his more illustrious team mate who has chosen the familiar luxuries of a five-star hotel.

"Roger's played twice before in the Olympics but this is my first one," he said. "I want to see how it is and enjoy it."

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