Judy Murray is confident that Andy Murray is on the right track to return toward the top of the game and admits she was “blown away” by his performance at the US Open.

In just his fifth tournament in 13 months, having had hip surgery in January, the former world No.1 played the best tennis of his comeback as he was narrowly beaten by Fernando Verdasco of Spain in the second round at Flushing Meadows.

And Judy, who was courtside to watch her youngest son, couldn’t believe how well he played.

“I thought he was amazing, I thought he was absolutely incredible,” she said. “It’s something like his ninth match and he just blew me away.

“The fight, you never lose that, that’s just within him. It’s still really early days in his [comeback] and he’s rusty, but like I said to him, rust comes off if you polish it. Work hard and polish it, it will come off.

“I was blown away with how well he played, sometimes it was just like watching him where he’d always been. There were rusty bits as well but that’s completely understandable. I thought he moved great, I thought it was incredible, very encouraging.”

The US Open was Murray’s first grand slam since last year’s Wimbledon and he will be just outside the world’s top 300 when the rankings are updated a week on Monday.

The Scot has a long way to go, with a lot of rehabilitation and hard work along the way, if he is to make it back to the top.

Murray tried to give his left hip injury time to heal last year without resorting to surgery but after six months in which the pain barely eased, he decided to have an operation in Australia in January.

Watching him in pain cannot have been easy.

“The great thing is being able to watch him playing again because you know how much it means to him, it’s been his life for such a long time - how difficult the last year, or 13 months or so has been, so actually to see him out there again and competing is great,” Judy said.

“You need a mindset that says it’s a work in progress and these are all stepping stones to where he wants to be. You would never expect any player to come back in where they left off after everything that he’s been through, so I think every step’s been positive, so it’s all good.”

When Jamie Murray was going through a rough period in his career and wondering whether he might retire, it was Judy who played a pivotal role, encouraging him to bring back his former coach, Louis Cayer.

This time, she has been just as important as Andy has dealt with not being on the court, being there whenever needed.

“I’ve always said that the emotional support for the top players is every bit as important as the technical and business support that you have,” she said.

“But it’s always been about finding the best people to deal with the situation that you’re in. You need to find people who understand how to rehab long-term injuries in top athletes.

“You need a framework, you need a routine and you need to know where it is you’re going because [of those people in his team] it’s not anybody’s area of expertise…in terms of rehabbing a long-term injury like this.”

The fact that Murray has been through some serious injuries in the past, including a knee problem when he was 16, a wrist injury in 2007 and back surgery in 2013, Judy said, meant he has not struggled as much as if he had never had an injury before.

“He knows what it’s like,” she said. “It’s just that this one has been longer and it’s probably been longer because he tried to rehab it conservatively to start off with and then had the surgery.

“In hindsight, that may have cost him, or did cost him, an extra six months. But these are things you don’t know.”

Andy is scheduled to play in Shenzhen later this month while Judy will also be in China, talking to coaches and taking her MissHits programme to Wuhan, where she and former grand slam winner Li Na will encourage young girls to get into the sport.

And it's Andy Murray's young girls who have also helped him, his time off the Tour giving him more time with his family, wife Kim and two young daughters, Sophia and Edie.

“I think that’s been the silver lining of it all, the amount of time he’s had with his family,” Judy said. “He wouldn’t have had that if he’d been on the tour and that’s definitely the silver lining of it. It’s been lovely for him.”