Roger Federer is looking forward to renewing his rivalry with Andy Murray in a blockbuster clash at London's O2 Arena.

The pair meet in Group A of the Barclays ATP World Tour Finals both boasting one win apiece and knowing the victor could secure a place in the semi-finals of the lucrative end-of-season tournament. Federer has won their biggest match to date, in the US Open final last year, and also their most recent meeting in Cincinnati but Murray can draw on memories of victories in Indian Wells and Doha this year as well as in the group stages of this event 12 months ago.

Federer said: "I hope we can live up to the expectations and play another good one. Obviously I expect a difficult match. It's always fun playing your rivals."

In Monday's matches, Robin Soderling pulled off the first shock of the tournament with a 6-4 6-4 victory over world number two Rafael Nadal.

The Swede, who only qualified for the tournament because Andy Roddick withdrew, was also the man who ended the four-time champion's winning run at the French Open this year and, after climbing into the top 10, he believes he is now becoming a real threat to the biggest names.

"I think I managed to play really well in the important points, which is something I think you have to do if you want to beat the top guys," he said.

"I played a lot of big matches this year, and I played well. I beat a lot of good players."

In contrast, Nadal lost the match primarily because he played poorly on the key points, Soderling breaking at 5-4 in both sets courtesy of sloppy errors from his opponent. With matches against Novak Djokovic and Nikolay Davydenko to come, the Spaniard is still well in contention for the semi-finals but, having admitted he is low on confidence, he let slip his expectation that he will only play two more matches at the tournament.

"I know, to be ready next year, I'm going to have one month, and these two matches," he said, before quickly adding: "Maybe more."

In the late match, defending champion Djokovic battled to a 3-6 6-4 7-5 victory over Davydenko in a near three-hour epic that was a repeat of last year's final.