Roger Federer admits he has been surprised at the speed of the hardcourt at the Olympic tennis tournament and believes it will narrow the gap between the top players and the rest of the field.

With leading players like Australia's Lleyton Hewitt, Argentine Guillermo Coria and 1996 Olympic champion Andre Agassi absent, the men's singles gold looks likely to come down to a fight between the Swiss world number one and second seed Andy Roddick.

Federer is not so sure. "There are lots of players who won't be nice to play against on this surface as it is so fast," the 23-year-old told reporters.

"My first practice was not so good. I felt the ball was flying, it bounces very high and I had to get used to it.

"It's going to be very hard you know. Maybe a few guys are missing like Agassi, Hewitt, Coria and some others, but the rest are here."

Ominously for his rivals, though, the Swiss added: "However, now I've played many hours on the court and I feel good.

"The last few practices were much better. I have started to find my rhythm."

Frenchwoman Amelie Mauresmo has compared the blue hardcourt at the Olympic Tennis Centre to the surface at the Australian Open - a good omen for Federer who won his first Grand Slam of the year in Melbourne.

Federer opens up against Russian Nikolay Davydenko on Monday. The Russian is ranked 56 in the world and will be no pushover.

"For me there are no easy matches around, it's very close to the level of the third round of a Grand Slam," Federer added. "It's going to be difficult for every tennis player to play well from the start."