Injured Murray forced to pull out of Monte Carlo Masters

The Scot's withdrawal had been expected after the 19-year-old was forced to retire from Monday's first-round doubles match with brother Jamie because of back spasms.

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Hit it and wince: Andy Murray suffered back problems while playing doubles

The new world number 10 had been due to face France's Marc Gicquel in the second round after being given a bye through the first round.

"I hurt my back in about the fifth game of our match," he told his website, andymurray.com. "I tried to play on but it got worse and worse and I couldn't stand up by the end of the tie-break.

"It's feeling better now that it was during the match, I've been taking some painkillers and had treatment and I can walk now, at least.

"I'm annoyed about it really as I was playing pretty well and my groin is feeling fine now.

"This is where the schedule is a problem I think, and not just because I got hurt. What do you expect when you are expected to go from medium outdoor hard, to very fast, indoor low-bouncing court, to very slow outdoor clay court?

"This is exactly the reason why guys like (Roger) Federer and (Rafael) Nadal won't play the Davis Cup, even though they love the competition, because it's tough on the body to keep changing surfaces.

"So for me, the Davis Cup - although it was great winning and I loved playing in Birmingham - is very hard to fit into your schedule."

Murray's place has been taken by world number 75 Guillermo Garcia-Lopez, of Spain, who faces Gicquel as a lucky loser.

The Scot yesterday moved to 10th in the world rankings after Tommy Haas failed to reach the US Clay Court Championships semi-finals.