Andy Murray prepared for tough encounter when rivalry with Juan Martin Del Potro resumes

First they played each other virtually to a standstill in a pulsating battle for Olympic gold in Rio.

Murray came out on top of that one to claim his second successive Olympic title but Del Potro got his revenge when they clashed again in the Davis Cup semi-finals a month later.

This time they played for five hours and seven minutes, the longest match of Murray's career, and it was Del Potro who prevailed to hand the Scot his first home singles loss in Davis Cup.

Del Potro, who went on to guide Argentina to their first Davis Cup title, was always going to be a danger lurking for one of the top seeds as he continues to work his way back up the rankings after wrist problems almost ended his career.

At his best, the 28-year-old has been one of the few players to consistently challenge the big four and Murray knows Del Potro's current ranking of 30 is misleading.

The Scot said: "That was obviously a brutal match we played in Rio, but also one of the most memorable that I'll have in my career regardless of what happens in the final few years of my tennis. We also played a great match in Davis Cup as well.

"It's a tough match, not an easy third round. He's, in my opinion, one of the best players in the world when he's fit and healthy.

"This year he's had a lot of tough draws. If you look at the matches that he's lost, he's played Novak a few times. He lost to Raonic in Delray Beach, Miami I think he lost to Roger.

"So because of the ranking that he has, he's in that bracket where he's met a lot of the top guys early on."

Del Potro has played a light schedule as he focuses on looking after his body but he was a doubt for the tournament because of back and shoulder injuries and struggled with a groin problem on Thursday.

Indeed, Del Potro might have been in trouble had opponent Nicolas Almagro not retired in tears with a knee injury at one set all.

Del Potro is optimistic he will be fit to face Murray, saying: "I will have two days in order to rest and recover. It's not new. Last year I had some problems with my groin. It's not a source of concern."

He is looking forward to having another crack at the world number one.

"We played great battles last year, one each," said Del Potro. "It could be another great battle if I feel good.

"Andy is one of the favourites to win this tournament. And now I know his game a lot, but I need to be in good shape and physically be stronger if we play a long match, long rallies.

"I'm happy with my level at this moment, my forehands and serves are working good."

Murray is getting used to having British company beyond the first couple of rounds at grand slams and this time it is Kyle Edmund who has joined him in the last 32.

The 22-year-old has used his huge forehand to bulldoze his way to straight-sets wins over Gastao Elias and Renzo Olivo and now meets South Africa's Kevin Anderson.

Edmund said of his big weapon: "That's my game. There's no point in having a shot like that and not using it. I've got to keep taking the initiative to bully players with it when I can.

"I know I'm going to have to play well to beat Anderson. He's obviously got a big game, he's a big guy. So Saturday I've just got to be on it."

Anderson broke into the top 10 after beating Murray at the US Open two years ago but is now down at 56 after injury problems.

He has been impressed by Edmund's rise to 49 in the rankings but is feeling positive about his own game after defeating Nick Kyrgios in round two.

Anderson, one of the tallest players on the tour at 6ft 8in, said: "He (Edmund) has had a lot of success in the last couple of years.

"He's really taken that step up and I'm expecting a very tough match. I think the clay suits a lot of areas of his game. I know he'll be very ready to go and he's a very strong competitor.

"I feel like each week I'm playing better and better tennis. My body feels really strong and healthy. For a while I feel like I've been hitting the ball as well as I've ever hit it in my career."