Andy Murray has admitted he wants to keep his mind on tennis as he prepares to take on German qualifier Matthias Bachinger in the second round of the US Open.

Murray insisted he arrived at the tournament in Flushing Meadows in the best possible shape but he was made to eat his words as he struggled with cramp on Monday.

The Scot rallied to eventually beat Robin Haase inside four sets but there are still doubts over his fitness.

Earlier this week Murray claimed the cramp could have been down to his nutrition and heat, and he will get to play in cooler conditions on Thursday night against Bachinger.

Murray had back surgery last September and he has yet to find his form since the enforced break. Roger Federer had his own back problems last season and Murray has agreed with the Swiss star’s comments that the mental side can take longer to recover than his body.

He said: “I think if you have a physical issue that’s hampering you, it’s very easy for that to take over your thinking when you’re on the court.

“It’s frustrating to not be able to do the things that you want your body to do and that distracts you from what you should be doing on the court, which is trying to beat your opponent, not how you have to move to your backhand side or your forehand side or whatever the issue is.

“I feel like I’m playing pretty good tennis and hopefully results will be not too far behind.”

The 27-year-old is currently 9.00 to win the US Open title with Dafabet but he could face Novak Djokovic along the way before a possible meeting with Federer in the final.