John McEnroe believes Andy Murray's new positive attitude can help the British No 1 emulate him as a grand slam winner.

The 21-year-old has enjoyed a sensational 2008, which has taken in a run to the US Open final and two Master Series title triumphs, in Cincinnati and Madrid.

Much has been made of Murray's improved physique and fitness, while he has also won praise for cutting out the petulant outbursts that sometimes marred his performances.

Seven-time grand slam winner McEnroe believes everything is now in place for the Scot to take the final step towards one of the sport's four major titles.

"When Andy Murray first came on the scene three or four years ago you heard people say that he could win majors, and he's putting all that together now," McEnroe said.

"Conditioning has been a big thing for Andy. He's in better shape and that allows him to believe in himself for longer. The second big change is that's he's now using his energy more positively and he doesn't allow the negative energy to get in the way as much.

"He keeps his focus more now and it's pretty obvious that if he can utilise those two things you get to see what he's capable of."

Murray will head into next week's season-ending Masters Cup in Shanghai as one of the favourites, particularly after the withdrawal of Rafael Nadal.

And McEnroe believes he has the game to trouble any of the planet's best players.

"What I love the most is how incredibly well he's moving. It's unbelievable. Most people can't move on the court like that and find the position and the angles that Andy's able to come up with,"he said.

"The way he's able to keep an opponent on his heels is really hard to do. I believes in the way he plays and he doesn't change his game plan - he mixes up his shots so well.

"He's got the hands and he can play up at the net as well and he's got a great brain and head for tennis."