Wimbledon 2014: Did an argument with Kim Sears put Andy Murray off his game?

Even his opponent, 23-year-old tennis star Grigor Dimitrov, noted something was off about the former champion.

'As soon as we started to warm up, I sensed that his game was not at the highest level,' he said.

Murray, 27, rubbished Dimitrov's comments, claiming he had simply had a 'bad day at the office' and pointed out that he had break points in the very first game.

But he lost to the Bulgarian in three straight sets during the quarter-final match, leading many to speculate over what went wrong for the player, who appeared on peak form as he breezed through the early rounds relatively unchallenged.

In the second set, Murray was heard muttering the words 'shut the f*** up' to himself. In the third, as he clung onto the game for dear life down 4-2, he was heard again saying: 'Five minutes before the f***ing match.'

Since then, reports suggest the colourful mutterings were the result of some sort of incident that took place as he prepared to take to the court. His comments seemed to be aimed up at the players' box, where his new coach Amélie Mauresmo, his girlfriend Kim Sears and his mother Judy Murray were sitting.

Murray left the grounds at SW19 in an All England Club car straight after his post-match interview, before he'd even changed out of his tennis kit.

According to a report in The Telegraph, Sears, 26, looked visibly upset as she made a swift exit from the player's box. She left Wimbledon alone.

The couple's separate exit stood at a stark contrast to Murray's defeat in the finals. After losing out on the title to Roger Federer, they left together.

Murray's spokesperson Matt Gentry, who was sitting in the players' box, said he had not heard Murray's utterances but agreed that the British number one had seemed a little 'off his game'.

'He always mutters to himself,' he said. 'Occasionally his language is a bit colourful and he does talk to himself. I think they were utterances of frustration.'

However, he gave no indication of what could have been the source of his frustration and is yet to respond to further request for comment.

Before the tournament had started, bookies closed bets on Murray proposing to Sears at Wimbledon, because they believed the couple were already engaged.

Engagement confirmation odds reached 7/2 - the same for Murray winning Wimbledon - leading William Hill to close the book.

'Gambles such as these are often proved correct so we believe that the announcement is imminent - but for the gamble to win he still needs to win Wimbledon,' a William Hill spokesperson told The Independent last week.

Murray's crashing out of Wimbledon is the latest in a long line of sporting disappointments for the UK this summer. It follows England's worst ever performance at a World Cup in history, after they were knocked out of the tournament in Brazil with just one point.