ANDY Murray's bid for a third straight Olympic singles gold medal ended before it began when he withdrew ahead of his first match with a minor thigh strain.

The Scot had been due to take on ninth seed Felix Auger-Aliassime of Canada on Sunday but was replaced on the order of play by Australian Max Purcell.

Murray had been upbeat about his prospects after an excellent doubles victory with Joe Salisbury on Saturday but experienced tightness in his quad muscle and was advised not to try to compete in both events.

Murray and Salisbury's form on Saturday, when they defeated French Open champions Pierre-Hugues Herbert and Nicolas Mahut, suggested they could be medal contenders.

The three-time grand slam champion said: "I am really disappointed at having to withdraw but the medical staff have advised me against playing in both events, so I have made the difficult decision to withdraw from the singles and focus on playing doubles with Joe."

Murray is the only tennis player ever to win back-to-back singles gold medals, and it appears highly likely his last chance to add to that haul has now gone.

Speaking after his doubles victory on Saturday, Murray had said: "I do like the conditions here in terms of how the court plays and everything.

"Obviously not an easy one against Felix but I've played well in the practice sets and the practice matches that I've had and obviously today was a good one for the confidence. I think I'll be all right."

But this is yet another physical setback for the Scot, who has been unable to play consistently since his comeback from hip resurfacing surgery two and a half years ago.

Liam Broady is now the sole hope for Team GB in the singles.

The 27-year-old, who is ranked 142, was a very late entry into the field following a raft of withdrawals but made the most of his opportunity, battling to a 7-5 6-7 (4) 6-2 victory over Argentina's Francisco Cerundolo in intense heat.

Cramp was beginning to set in when Broady, from Stockport, finally made it across the line after more than three hours having held two match points in the second set.

He said: "It was brutal. It's probably one of the first three-set matches I've played that has gone over three hours and what conditions to do it in. The third set comes down to a battle of wills and thankfully I won that today."

Broady must now try to recover ahead of a second-round clash with seventh seed and Wimbledon semi-finalist Hubert Hurkacz.

He said: "My main concern was not wanting (people) to look at me and think I'm making up the numbers. I'm here to compete, I'm here to play and to win matches. I was just hoping I'd acclimatise to the time zone and the heat quick enough.

"It's been unbelievable, once in a lifetime. I've never played an event like it and hopefully will do one more time in my career. I'm just taking everything in and really enjoying it."