LONDON - Andy Murray's hopes of winning the ATP World Tour Finals were dealt a double blow when he lost his opening group match to Spain's David Ferrer and then warned he could have to withdraw from the tournament with a groin injury.

The 24-year-old Scot produced an error-strewn display in a 6-4 7-5 defeat, his first to Ferrer on any surface other than the Spaniard's preferred clay, slumping to defeat in their opening Group A clash in exactly two hours at the O2.

Murray often looked leaden-footed and lacked any spark despite leading in both sets.

The world number three needed treatment at the end of the first set and although he was able to carry on without calling for the physio again, he could find no way through the formidable defences of the 29-year-old from Valencia.

"Yeah, I mean, I had a problem with my groin. I have to see how it goes for tomorrow," Murray, who arrived in great form after a recent 17-match winning streak that included three consecutive titles in Asia, told reporters.

"I'll decide tomorrow whether or not I keep playing. If it wasn't slams or this event, I wouldn't have played."

Murray, if he does recover, could have to beat both in his remaining matches to qualify for the semi-finals of a tournament that ranks just below the grand slams in terms of prestige and importance.

Ferrer, who was runner-up at the season-ender in 2007, is exactly the kind of player Murray would have least liked to have faced given his physical condition.

One of the game's most durable players, Ferrer scampered all over the court to frustrate Murray's attempts to take charge of the contest.

The Scot made 44 unforced errors as he attempted to break down Ferrer. He achieved early breaks in both sets but on each occasion he tamely surrendered his own serve immediately with some elementary mistakes.

"I think it was important to start with a win," Ferrer told reporters. "I think he had some little problems, but not too many strong problems because he played the whole match."

Djokovic scrapes past Berdych to win opener

World number one Novak Djokovic survived a match point on his way to a 3-6 6-3 7-6 defeat of Tomas Berdych in his opening group match at the ATP World Tour Finals on Monday.

The Serb, winner of three of the year's four majors, was given a thorough grilling by the hard-hitting Czech before sealing victory in two hours and 38 minutes to join Spain's David Ferrer on one win in Group A.

Berdych, whose only previous victory against the Serb came at Wimbledon last year, was left kicking himself after wasting a chance on his forehand when Djokovic served at 5-6, 30-40 in the decider.

He then fell apart in the tiebreak, gifting Djokovic several cheap points with rash errors and his opponent seized his opportunity, clinching victory at the first attempt.

Rafa Nadal and Roger Federer both won their opening Group B matches on Sunday, although they were pushed to three sets against Mardy Fish and Jo-Wilfried Tsonga respectively.

Nadal and Federer face each other for the 26th time in their careers on Tuesday, although it will be the first time they have met in a round-robin scenario.