British number one Andy Murray is guaranteed a shot at a medal in Rio after overcoming Steve Johnson to set-up a semi-final showdown with Kei Nishikori.

The defending Olympic champion has struggled to hit top form in South America over the last week but continues to do enough to keep moving forward.

The 29-year-old saw off his American opponent 6-0 4-6 7-6 (2) on Friday in tough conditions to book his place in the last four.

Murray is looking to make history by becoming the first man to win back-to-back Olympic titles following his success on the grass courts at London 2012.

The Scot admitted that conditions have affected practice sessions but feels he is starting to get into the swing of things at the business end of the tournament.

Murray said: “We didn’t get to hit balls before the match because of the rain.

“He just started slow and came back into it, played very much better. These are quicker courts so I expected a tough one.

“It didn’t feel too slow to me. It was quite lively. It’s the wind that’s making it challenging. It’s very breezy out there. The courts are wide open.”

The three-time Grand Slam winner insists there is a different feeling around the Olympics and hopes he can continue his journey to claim a medal.

He added: “It’s been difficult in tough conditions, after great starts.

I was close to going out. Some times that can work in your favour. But you want to play a little bit better, loosen up a little bit. “It feels different. This is special.

We don’t get this opportunity all of the time, competing for medals for your country, that’s special. For me, it’s got nothing to do with having won the gold medal in London.

It’s just about trying to win more medals for your country and the team.” Nishikori can be backed at 3.10 to make it to the Olympic final, while Murray is priced at 1.33 to progress to the gold medal match.