World number three Andy Murray was forced to withdraw from the ATP World Tour Finals on Tuesday after failing to recover from a groin injury.
Murray was told he would need up to 10 days off after suffering the injury in practice last week and, although he initially ignored that advice to play David Ferrer in his opening match at the O2 Arena, he has now decided to pull out of the season finale less than 24 hours before he was due to face Tomas Berdych.
Murray, who will be replaced by Serbian Janko Tipsarevic, knew he was in trouble during Sunday's lacklustre defeat against Ferrer and he said: "It was one of those things where you kind of hope that things are going to get better, but reality was that wasn't ever going to happen.
"I woke up this morning still sore. I was just trying to find reasons why I should try to play.
"But there was no real positive of coming out and playing because on Sunday I was really unhappy on the court. I wasn't enjoying it at all.
"This is one of the best tournaments in the year, one that I think me and all of the players look forward to playing.
"I couldn't give anywhere near my best. So that's what was disappointing. It would probably do myself more damage by playing than not."