Andy Murray was delighted to come through a significant mental test as he battled past Mackenzie McDonald in round one of the Citi Open.

Although he returned from hip surgery in June, Murray decided not to compete at Wimbledon as he believed it was "too soon" to compete in five-set matches.

The former world number one is now looking to regain match sharpness ahead of the US Open and could take positives from a 3-6 6-4 7-5 victory over McDonald on Monday, even though he was well below his brilliant best.

"I wasn't dictating many of the points. I wasn't hitting the ball that cleanly. I just fought and tried to make it tough for him," Murray was quoted as saying by the ATP World Tour's official website.

"I made a few little adjustments here and there. But mentally, it was a big one to get through.

"It could have gone either way. Obviously if you lose a match like that, it's a tough one."

Murray's serving was poor at the beginning of the contest, but he gradually raised his level before converting his seventh match point and celebrating passionately.

He will now face Kyle Edmund - the man who has succeeded him as Great Britain's number one and beat Murray in Eastbourne last month.

"I think I cut the unforced errors down. I started to serve a little bit better," Murray added.

"I started off the match serving very poorly. I was struggling on my serve and didn't feel like I had much rhythm. I haven't played in the darkness or under the lights in a very long time and I felt like my rhythm was off on serve, my timing a little bit.

"That started to get a bit better as the match went on, so that helped... I made a few less mistakes, but I would like to play better tennis in the next match."