Andy Murray has hinted at the possible cause of his poor performance in yesterday's straight sets defeat to Grigor Dimitrov at Wimbledon.
The Scot had hardly put a foot wrong in his first four matches, but he never approached his best tennis against the Bulgarian.
During the game Murray, 27, was spotted by some onlookers swearing in the direction of the players' box, and reportedly shouted: "Five minutes before the f****** match."
It is not clear what his comments were referring to, although Murray's match did start earlier than normal.
Play began on Centre Court at noon rather than the usual time of 1pm to catch up with the schedule after rain delays, and the match before Murray's ended after just 57 minutes.
Writing in his BBC column today, Murray said: " There was nothing different in the build-up and no reason to expect that kind of performance.
"The timings changed a bit because we played the quarter-final pretty early compared with some of my other matches, but my routine was the same and I practised with James Ward both days."
Dimitrov suggested after the game that he knew from the warm-up that Murray would not be at his best.
"I think it's just a feeling," he said. "I have practised quite a few times with him and I know how he is striking the ball when he is at his best, I know how he is playing when he is not at his best. I think it's just a feeling that I had."
Murray revealed he would now go back to Miami to work hard in training.
" The game always improves and gets better, and I know I have things to work on. I plan to be back on the practice court and in the gym soon," he said.
Murray's spokesman Matt Gentry was sitting in the players' box and said he did not hear Murray's outburst.
But he added: "Occasionally his language is a bit colourful and he does talk to himself.
"He does look at the box - he likes to see people he knows rather than a face in the crowd. I think they were utterances of frustration. It would have been just frustration, to be honest with you.
"He was quite circumspect after the match."
As the players walked off a stunned Centre Court, Murray reminded his opponent that they should bow to the Royal Box, where the Duke and Duchess of Cambridge were sitting.
Murray said: "We spoke about it before the match and we were given the instructions to bow. It used to be a tradition always. Now it's changed unless there's royalty in there.
"But, yeah, that's something we talked about. I made sure to remind him when we were walking off the court, because I can imagine for him it was the first time he's been in the semis of a slam, so just to make sure that we did it when we walked off."
The spotlight moves to the ladies' singles today with both semi-finals taking place on Centre Court.
The Royal Box is set to be filled with a host of stars including a ctor Colin Firth, comedian Miranda Hart, broadcaster Sir Michael Parkinson, TV presenter Cilla Black and singer Sir Cliff Richard.
They are due to be joined by Lord Patten, actor Eddie Redmayne and swimmer Ian Thorpe.
The Centre Court crowd will watch f ormer champion Petra Kvitova face fellow Czech Lucie Safarova before Canadian Eugenie Bouchard plays Simona Halep.
Murray's brother, Jamie, is also in action on the showpiece court in the third round of the mixed doubles.
Forecasters are predicting a dry, bright and warm day at the All England Club, with a maximum temperature of 27C.