When Andy Murray was asked the inevitable question yesterday, he gave the inevitable answer. Will he be fit in time for the start of Wimbledon in four days' time? "I don't know."

The Madame Tussauds waxwork of him that he unveiled yesterday might have been more forthcoming, though given the thick veil of secrecy which currently surrounds Murray's fitness at the moment, it has probably been made to sign a confidentiality agreement.

Yesterday all questions about the wrist which Murray injured in Hamburg over five weeks ago were strictly off limits, but he did break his own vow of silence to give the latest clue in the guessing game of whether the country's No.1 player will be fit in time for the start of his home grand slam.

"I can serve and volley fine; it's just the ground strokes that are taking time," said Murray, who practised at the Lawn Tennis Association's grass courts at Roehampton with Scottish teenager Graeme Dyce yesterday, as Murray's coach Brad Gilbert looked on.

The practice session with Dyce was probably more taxing than the 20 minutes he spent on court at Stoke Park later in the afternoon, knocking up with a 10-year-old competition winner, but neither came close to the physical and mental demands of a best-of-five sets match at Wimbledon.

As No.8 seed for the tournament - the highest seeding he has had at a grand slam - Murray will have to do more than play pat-a-cake tennis for the cameras. He may yet have to listen to fellow players like the American James Blake, who yesterday added his voice to those warning Murray that he could risk further injury by playing if he is not fully fit.

"I know from experience that it's dangerous to play with a small injury. I've done it and I know what it's like," said Blake, the world No.9. "You're so competitive and the adrenaline starts so that no matter how careful you want to be, you're not.

"You're never careful because you want to win so badly. The adrenalin is pumping so much that you don't know when to stop and you can possibly end up making the injury worse.

"In the match you don't feel the pain but afterwards you do. It could then become a chronic thing that keeps you out for longer."

The United States have not produced a grand slam title winner since Andy Roddick stormed to the US Open in 2003, leading to concerns that the sport is in crisis across the Atlantic.

Blake is confident that both he and Roddick have a better chance of triumphing at Wimbledon than Murray.

"In my opinion, Andy Roddick is the second best grass player in the world. I would make him second favourite after Roger Federer. I'd like to think my chances are better than Andy's too."

Blake was speaking at the launch of Turbo Tennis', an initiative that reduces competitions to a single afternoon and matches to just 30 minutes.

Murray will be among the competitors for the UK leg to be staged at the O2 Arena on September 15 - alongside Blake, Tim Henman, Jamie Murray, Goran Ivanisevic and Pat Cash.

"I don't think tennis needs a change to overhaul the game but something like this can show different ideas and perspectives and maybe attract younger fans," said Blake.

"This excites younger fans who may become fans of certain players and then go and watch Grand Slams."