London:Roger Federer and Rafael Nadal have proven to be vulnerable this year, and Novak Djokovic removed another layer of their invincibility recently by beating both players ahead of the ATP World Tour Finals.
That, however, doesn't mean the third-ranked Serb - arguably the hottest player on tour heading into the season-ending tournament at the O2 Arena - is immune to feeling nervous before facing either of them.
"The one who says there is no fear at all will lie to you," said defending champion Djokovic, who is in Group B of the round-robin tournament with Nadal. "There is always some kind of nervousness in yourself before the match."
The difference now is that Djokovic won't settle for just losing gracefully.
"I have the feeling that I want to win," the 22-year-old Serb said at a media round-table. "When I get to play them, it's a big challenge for me."
Djokovic will open against Nikolay Davydenko on Monday. Robin Soderling is also in the group, and faces Nadal on the same day. The matchups for the second and third rounds have yet to be announced, so Djokovic could end up playing Nadal in a match that will decide who reaches the semifinals.
"He is the player who is playing best," said Nadal, who is back to full strength after a season affected by injuries. "But you never know. Every tournament is different."
Federer is playing in Group A and opens Sunday against Fernando Verdasco. Andy Murray will take on U.S. Open champion Juan Martin del Potro in the first singles match of the weeklong indoor tournament.
"At the very last tournament of the season, we could be sent home packing with three defeats," Federer said. "But we can also go home having the best feeling in the world after beating all your closest rivals you've had through the year.
"This year is really wide open."
Nadal started the major season by beating Federer in five sets to win the Australian Open. The second-ranked Spaniard then lost for the first time in his career on the clay courts of Roland Garros, falling to Soderling in the fourth round of the French Open.
Federer won that title in Paris, and then reclaimed his Wimbledon trophy by beating Andy Roddick 16-14 in the fifth set. Roddick qualified for the season-ending tournament for the top eight players in the world, but he withdrew because of a left knee injury and was replaced by French Open finalist Soderling.
At the U.S. Open, Federer was forced to go another five sets but lost in the final to Del Potro, who eliminated Nadal in the semifinals.
But while Federer was nearly back to the dominant player that won five straight Wimbledon and U.S. Open titles, it was Nadal that had what many consider to be an off year despite his one Grand Slam tournament victory.
Federer is not convinced.
"I don't think we should exaggerate," Federer said of Nadal. "The guy has had the most incredible first five months of the year. He dominated the first part of the year.
"That's why I don't think it has been that tough of a year. ... He won the Australian Open, he played some incredible matches this year and he's still got a chance to finish very strong here and still finish the No. 1 in the world. To me it doesn't seem like a horrible scenario to have, really."
The champion of the tournament in London could earn $1.63 million by winning every match. Money, however, is not what drives everyone.
"When you're playing the matches, it doesn't cross your mind at all. It's not something that gets your nerves going," said Murray, who won six titles in 2009 but is still chasing his first major victory. "It's just sort of something that comes with winning, so you got to take care of that part first."
The breakthrough man this year, though, was Del Potro.
The Argentine has moved up to No. 5 in the world rankings and is closing in on fourth-ranked Murray. He also won two other titles this season to complement his first Grand Slam title.
"The next step will be to be No. 3 or No. 2 in the world," Del Potro said. "I'm working towards that, to do it in the next year. I hope it will be another season like 2009."