Andre Agassi says the next 12 months will decide whether Andy Murray can go on to become the world's best tennis player after he predicted an end to the dominance of Roger Federer and Rafael Nadal.

The American former world No 1 has always had faith in Murray's ability and tipped him to win Wimbledon and the US Open earlier in the year. The world No 3 failed to live up to expectations at either tournament and the emergence of Juan Martin Del Potro, who won at Flushing Meadows, has led some to question whether Murray has what it takes to dominate the game. Murray is the only player in the world's top six not to have won a grand slam.

"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," Agassi said. "He has a lot of reasons, motivations and skills that can 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.

"We have possibly the changing of the guard. You have those top two who are now losing ground to the likes of [Novak] Djokovic and Murray and Del Potro. When I look at Murray's game compared to the other players, he has what it takes to win and to win against anybody on any surface."

Last week Murray pulled out of the Shanghai Masters after deciding not to risk his injured left wrist. He is likely to return at the inaugural Valencia Open in Spain from November 2, to satisfy his commitments at the ATP. However, Agassi believes despite his injury problems, Murray has matured into one of the game's fiercest competitors.

"In the beginning he had an attitude that worked against him," Agassi said. "It was a fire, it was a spirit, you could tell that was a crucial wiring to the way he played. 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.

"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."

Agassi is due to play Pete Sampras in an exhibition match in New York on October 25. It will be the first meeting between the two since the 2002 US Open final, which Sampras won.