Sweden’s Robin Soderling repeated his Roland Garros success over Rafael Nadal Monday, defeating the Spaniard 6-4, 6-4 in the first Group B match of the Barclays ATP World Tour Finals, staged at The O2 in south-east London.

Soderling’s triumph both denies Nadal his 400th tour-level match win and seriously hinders the Mallorcan’s prospects of defending his ATP World Tour Champion crown this season.

World No. 1 Roger Federer increased his lead to 1,145 points over Nadal after his hard-fought victory against Fernando Verdasco Monday and could now be just one win away from reclaiming the year-end No. 1 spot in the South African Airways 2009 ATP Rankings – a position he held for four years between 2004-2007.

Nadal can now only gain a maximum of 1,300 points, should he win his remaining two round-robin matches and clinch the title, meaning Federer would need to either win just one more round-robin match, or go 1-2 in round-robin play and reach the final to finish as ATP World Tour Champion.

A frankly honest Nadal said afterwards that he thinks the contest is virtually over. “I think the chances I have are not here, not to be No. 1. My level right now I think is not to be No. 1.”

Federer is looking to become only the second player in the history of the South African Airways ATP Rankings to have held, lost and then regained the ATP World Tour Champion title. Ivan Lendl held the year-end No. 1 South African Airways ATP Ranking between 1985-87, then finished second behind Mats Wilander in 1988, before reclaiming the top spot at the end of 1989.

Following Soderling’s victory over Nadal in the fourth round at Roland Garros, and the Tibro native’s renowned prowess on indoor hard-courts, much was expected of him in his fifth meeting with Nadal. He did not disappoint, employing a high-risk strategy of keeping the points short by going for winners – a tactic that paid dividents the majority of the match.

“I think I was hitting the ball well today,” assessed Soderling. “And I think that's kind of a little bit how I have to play against Rafa to have a chance to beat him. It's tough to keep on playing these long rallies every time, because he's a great fighter, and he's moving really well. So I tried to keep the points short, and it worked today.”

Soderling took advantage of a slow start by the World No. 2 to quickly establish a 3-0 lead, but could not hold the Spaniard at bay for long as he hit back to level at 3-3. With the pressure mounting at the close of the set, though, Nadal could not rein in his errors and a forehand long saw him surrender the first set.

Nadal looked to be back on track as he engineered an early service break in the second set by catching Soderling out at the net and smashing the ball past him. However, more errors from the Spaniard let him down in the following game as Soderling levelled and it was the Swede who broke decisively, hitting a stinging backhand winner cross court to earn match point in the 10th game and converting as Nadal miss-timed his backhand after 98 minutes.

“Well, I felt pretty good,” said Soderling. “For me it's always tough. Every first round match in every tournament for me is the toughest one. So I was a little bit nervous in the beginning. But I got off to a very good start with an early break, so that helped me a lot.”

The 23-year-old Nadal was bidding for his 400th tour-level match win and currently sits on a 399-89 mark. He was also denied the milestone win in a semi-final defeat to Novak Djokovic at the BNP Paribas Masters in Paris (Bercy) two weeks ago.

“I think I didn't play really bad. I played okay,” assessed Nadal. “But in the important moments, I didn't have the necessary calm, so I had few mistakes. He is a big player in this surface, so is difficult. If you are not completely calm and playing very well in that moment, it's really difficult to win, and today I didn't play in this way in those moments.

The reigning Australian Open champion has been hindered in the second part of the season by knee tendonitis, that forced him to relinquish his Wimbledon title defence, and an abdominal strain picked up on the North American hard courts. He has not won an ATP World Tour title since May, when he defeated Novak Djokovic in the final of the Internazionali BNL d’Italia in Rome.

“I am working really hard to come back at my best level,” said the left-hander.” I think I'm not far away from my best level. But I need little bit more confidence and more calm in those moments. This year is going to be extremely hard to finish really well. But I’m going to work very hard to start next year very good. I believe in myself, that I can come back playing really well next year.”

The 25-year-old Soderling – a late replacement for the injured Andy Roddick - earned his place in the season finale for the first time, largely due to his runner-up finish at Roland Garros (l. to Federer) – his first appearance in a major final. The World No. 9, coached by countryman Magnus Norman, also won his fourth ATP World Tour title at the Catella Swedish Open (d. Monaco) in Bastad and has compiled a 48-19 match record.

Soderling is the first Swede to compete at the year-end championship since Thomas Johansson came in as an alternate in 2002. Thomas Enqvist was the last Swede to qualify and play at least three round-robin matches in 1999.