Andre Agassi believes the next 12 months will define the career of British number one Andy Murray.

Agassi tipped the current world number three to triumph at Wimbledon and the US Open earlier this year and was surprised the 22-year-old was unable to win his maiden grand slam at SW19 or Flushing Meadows.

But now, with the emergence of US Open champion Juan Martin Del Potro, Agassi reckons it is time for Murray to live up the hype and undoubted talent and add a major to his 13 ATP titles.

Murray is the only player in the world's top six who has now won a grand slam, with 21-year-old Del Potro joining Roger Federer, Rafael Nadal, Novak Djokovic and Andy Roddick.

"I think that in the beginning he had an attitude that worked against him. It was a fire, it was a spirit, you could tell that was a crucial wiring to the way he played," said eight-time grand slam winner Agassi.

"Whether it was good or bad, it was significant in his game and in his matches and most of the time it hurt him.

"But very recently you have seen him use this to his advantage. You have seen him become a phenomenal competitor and you have watched him use that anger and negativity to push himself.

"He has used it in a positive way over a long period of time. He just has another hill to climb here.

"Whenever he expects a lot from himself it really wrestles with your weakness the most and now he is starting to expect himself to win and it has put himself in a simple position - either I am going to step up to the plate and I am going to accept this responsibility and continually push myself, or it's going to work against him and get the better of him.

"It is a very fine line, it is like a razor's edge you live on as a professional athlete, especially a professional athlete who has no-one else to pass the ball to - you are out there by yourself.

"This is going to be a crucial time in his career and I predict the next year will determine his career one way or another. He has one big opportunity in front of him. He has a lot of reasons, motivations and skills that can get help him to accomplish a great deal, but he has to be willing to push to get over the next hump.

"Do I think he can do it? Absolutely. Do I expect him to do it? I really do. When I look at his game compared to the other players, he has what it takes to win and to win against anybody on any surface.

"Nadal has the advantage on the clay if he is healthy. But Murray, I don't favour anybody over him on any surface at any time if he brings to the table all he can."

Agassi was speaking from New York ahead of an exhibition match against Pete Sampras at The Venetian Macao Tennis Showdown on October 25. It will be the first meeting between the two since the 2002 US Open final, which was won by Sampras in his last ATP Tour singles match.