LONDON - World No 1 Novak Djokovic clawed his way to victory over Tomas Berdych in his opening match at the ATP World Tour Finals on Monday, but Andy Murray's prospects look bleak after a groin injury flared up in his shock defeat by David Ferrer.

Djokovic, who arrived in London with question marks over his right shoulder, showed all the qualities that have made him the year's dominant force, digging himself out of trouble to win 3-6, 6-3, 7-6 (3) after saving a match point deep in the decider.

Murray, the hottest player in the world since the US Open, was tipped by many to win the title in London but after a 6-4, 7-5 defeat to bustling Spaniard Ferrer he faces an uphill battle to reach the semifinals even if he can continue.

The 24-year-old Briton said he was "gutted" after the injury he sustained while practising for the season-ender hindered him during an error-strewn two-hour defeat.

"Yeah, I mean, I had a problem with my groin. I have to see how it goes for tomorrow," Murray, who had never lost to Ferrer on any other surface than the Spaniard's favorite clay, said. "I'll decide tomorrow whether or not I keep playing. If it wasn't slams or this event, I wouldn't have played."

While the atmosphere in the O2 was a little flat as Murray labored, it was electrifying in the night session as 17,500 fans, many waving Serbian and Czech flags, crammed into the huge arena that will stage the event until 2013.

After losing the opening four games, Djokovic gradually found his range although he still had to recover from 4-2 down in the decider before Berdych finally ran out of firepower.

"That was the toughest match since the US Open," Djokovic, who won three of the year's majors and grabbed the No 1 ranking from Rafa Nadal, said. "I wasn't very satisfied with my performance but a win is a win."

Despite having blue tape plastered over his shoulder, Djokovic said he had suffered no recurrence of the injury that forced him to withdraw from the Paris Masters this month.

"Something I'm happy about is my condition," he said. "I haven't felt any pain in my shoulder. I'm exhausted because it was three hours but I feel physically fit."

Murray led in both sets but never looked comfortable despite winning all five of his previous hardcourt clashes with the 29-year-old baseline slugger.

There were some occasional flashes of brilliance but too few to prevent Ferrer earning a deserved victory.

The Scot made 44 unforced errors as he attempted to break down Ferrer's formidable defenses and needed treatment at the end of the first set. "I think it was important to start with a win," Ferrer said. "I think he had some little problems, but not too many strong problems because he played the whole match."

Reuters