Andy Murray recognises that he must keep capitalising on his rivals' dips in form if he is to continue winning Grand Slams.

The world number two has made the most of Novak Djokovic's slump in form over the summer, winning Wimbledon and the Olympic gold.

Djokovic, along with Rafael Nadal, has struggled with injury at the US Open, with Roger Federer out for the season with a back injury, but Murray knows he must keep his focus to go all the way in New York.

"I have capitalised on a few opportunities," Murray said. "When some of the other top guys maybe hadn't played or struggled or lost, it's important I have taken those chances when they have come my way, which is good.

"Becoming a parent has changed my perspective a bit on things. I feel a little bit calmer than maybe I did in my past about my tennis and how important tennis is in my life.

"It's still extremely important, but it's not the most important thing. I think having Ivan back on my team has been great and has helped me a lot.

"There have been a number of changes this year and I think all of them coming together at the same time has made for a successful few months."

Murray's greatest obstacle may yet be the weight of expectation, given he is now considered the favourite in the draw, even with the likes of Stan Wawrinka and Juan Martin del Potro lurking in his half.

Fifth seed Milos Raonic, who beat Federer at Wimbledon before losing to Murray in the final, crashed out on Wednesday after admitting "nerves and stress" had left his body riddled with cramp.

Murray is one of the fittest players on tour, meticulous in his preparation, but he too experienced cramps here two years ago, when he survived a brutal contest with Robin Haase.

"There is the psychological aspect of it," Murray said. "The stress that you might put yourself under and the nerves that you feel can cause that.

"I think most players have gone through it and for some reason it seems to happen more at this event, I think, than at the others.

"I don't know if that is because of the humidity or maybe players are coming in here more fatigued at the end of a long season, a long stretch. I don't know."