ATP World Tour Finals Venue: O2 Arena, London Date: 22-29 November Tournament coverage: Live on BBC Two, 28/29 November, 1430 GMT; every match live on BBC Radio 5 live/5 live sports extra; live text commentaries on BBC Sport website; live coverage every day on Sky Sports
Soderling ended Nadal's 31-match unbeaten run at the French Open in May
By Piers Newbery
BBC Sport at the O2 Arena
Sweden's Robin Soderling enjoyed his second shock win of the year over world number two Rafael Nadal with a straight-sets victory at the ATP World Tour Finals in London.
The eighth seed repeated his stunning effort at the French Open with a 6-4 6-4 win in the opening Group B match of the round-robin phase.
Soderling only made it into the season finale for the world's top eight players after Andy Roddick pulled out with an injury, but the 25-year-old has put himself in pole position to reach the last four.
In the same group, defending champion Novak Djokovic plays seventh seed Nikolay Davydenko later on Monday in a repeat of last year's final.
Nadal refused to make any excuses after the defeat, insisting that he was 100% fit and dismissing any suggestion that he had been after revenge for Roland Garros.
"I think I didn't play really bad, I played OK," he said. "But in the important moments I didn't have the necessary calm - I played shorter in the important moments. That's the reason he beat me.
"He's a big player on this surface, so it's 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 at that moment."
A clearly thrilled Soderling said that holding his nerve at the decisive moments in each set had been vital.
"Especially today, I managed to play really well on the important points which is something you have to do if you want to beat the top guys," he said.
"I've played a lot of big matches this year and played well, beaten a lot of good players, so I'm sure I've improved that part of my game."
Soderling had arrived in London with little expectation surrounding him, but relatively free of pressure and coming off the best year of his career as he rose to nine in the world.
At 6ft 4ins and with a big serve and heavy forehand, his game is more naturally suited to the O2 Arena conditions than Nadal's, and three of the Swede's four career titles have been won indoors.
Nadal, in contrast, could end the year as world number one with a good run in London but has been searching for his very best form since the knee injury that forced him to miss Wimbledon, and the subsequent abdominal problem that hurt his US Open campaign.
After a rapturous reception from the 17,000 crowd, Nadal - like Roger Federer the previous day - made a poor start.
A couple of blistering winners in the second game let any spectators unfamiliar with Soderling's game know what they were in for as he broke at the first opportunity, and a vicious forehand winner and an ace took him to 3-0.
Nadal might have been struggling for form in recent weeks but his fighting qualities have not wavered, and he pounced on the first Soderling errors to get back on serve in game five.
But a mark of Soderling's improvement this year has been the ability to maintain his composure in the key moments, and it was the Swede who turned the screw in game 10.
Nadal consistently struggled to find anything close to his best form
At 5-4 and 30-30 he guided a backhand into the corner that Nadal could not deal with, and the Spaniard then went long with a backhand on set point.
Nadal appeared ready to turn the match around when he broke first in the second set, beating his chest in celebration after a smash took him 2-1 ahead, but Soderling responded immediately by moving to 0-40 and converting his third break point when Hawkeye went against the Spaniard.
Both men were now threatening on their return games and game five was an epic, with Soderling coming through 12 deuces and saving two break points - the first with a 132mph ace.
As in the first set, Soderling had the advantage of serving first and found himself just four points from victory at 5-4 in front.
Again the pressure told on Nadal as he leaked a couple of backhands over the baseline for deuce and then another to face match point, but Soderling's forehand cracked first in a nerve-jangling baseline exchange and the second seed clenched his fist in celebration.
It was only a momentary respite, however, and Soderling ripped a magnificent backhand winner to earn a second match point before Nadal made another backhand error to give the Swede victory in one hour and 38 minutes.
After the match, Nadal said he would not rule out his chances in this tournament with two group games still to play, but admitted he had all but given up on his chances of overtaking Roger Federer to end the year as world number one.
"If you still want me to talk about number one I can, but I think it's not the right moment," he said. "My level right now I think is not to be number one."
There was a shock in the doubles for the second day running as seventh seeds Max Mirnyi and Andy Ram defeated second seeds Mike and Bob Bryan 6-4 6-4, after top seeds Daniel Nestor and Nenad Zimonjic lost their opener on Sunday.
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