Andy Murray has scoffed at John McEnroe's suggestion that this week's US Open represented his best chance of winning a Grand Slam.

McEnroe, a former US Open champion turned commentator, has tipped Murray to win the title and claim his first Grand Slam title.

The American said Murray was in great form after winning a lead-up event in Cincinnati while his three main rivals, Roger Federer, Rafa Nadal and Novak Djokovic, all had health concerns.

But Murray, who has played in three Grand Slam finals but lost them all, said McEnroe's comments were unhelpful.

"It's a silly thing to say," the Scotsman told a news conference.

"I have a chance of winning for sure. Whether it's my best chance or not, no one has a clue like that."

Murray is seeded fourth at Flushing Meadows but is the only player amongst the top four not to have won a major. To win the title, he faces the prospect of having to beat two of his great rivals on the final weekend.

"Someone like John who has played hundreds and hundreds and thousands of matches probably knows that one bad day and you can put yourself out of the tournament," Murray said.

"Especially towards the latter stages when you're playing against ... three of maybe the three greatest players ever. You're going to have to play an incredible event to win.

"So I feel like I'm ready to do that. But to say it's my best chance, no one knows."

Murray will open his campaign against India's top-ranked singles player Somdev Devvarman on either Tuesday or Wednesday.

The pair have never met before and the odds are heavily stacked in the Briton's favour but he said he was not taking anything for granted.