Andy Murray lost his Wimbledon title after an uncharacteristic performance on Centre Court where he appeared to be distracted by external events.
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---king match."
It led to speculation that there may have been an incident prior to the match which distracted the reigning champion.
Others reported hearing him shouting "shut the f--k up" towards the players box between points.
It is not clear what his comments were referring to, although Murray's match did start earlier than normal.
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."
ITV News was also able to record footage of Murray arriving at Wimbledon ahead of yesterday's match. In the clip, the defending champion appears upbeat.
Murray lost in straight sets to Gigor Dimitrov who claimed he "sensed" something wrong with the Scot during the warm up. However, Dimitrov conceded a lack of close games last week may have counted against Murray.
On his game yesterday the 27-year-old said: "I started the tournament well. I was playing good tennis. Today was a bad day from my side. I made many mistakes and then started going for too much and taking chances that weren't really there.
It was a tough day all around."
Former Champion Goran Ivanisevic was also full of praise for Murray's opponent.