Former Wimbledon champion Goran Ivanisevic believes Britain's Andy Murray has what it takes to be the world number one.
Murray ended 2006 ranked 17th after his first full season on the ATP Tour and Ivanisevic says he can go higher.
"He can be number one," he told BBC Sport. "But I don't know when. He can easily be top 10 next year.
"He is already very close to the top 10 and must continue what he's doing. He's a great player and will get better."
Ivanisevic, who retired in 2003, believes bringing American coach Brad Gilbert on board to advise Murray will benefit the Scottish 19-year-old.
"Brad was a good player and he's a great coach," said Ivanisevic, who is in London to play in the Masters tournament at the Royal Albert Hall. "He knows what he's doing.
"Murray has got the talent, but he's young and needs someone to tell him things. You have to have more than one pair of eyes.
"The Grand Slam for Roger Federer will be very tough because Rafael Nadal is better on clay"
"The better he gets the more pressure there will be. He is already a great player and he will become even better."
Murray's progress in 2006 saw him beat Lleyton Hewitt to claim his first ATP Tour title in San Jose.
He also reached the last 16 at Wimbledon and earned a landmark win over Roger Federer in Cincinnati - the only player apart from Rafael Nadal to beat the world number one this year.
Ivanisevic expects Federer to dominate again in 2007, but is cautious about his chances of becoming the first player since Rod Laver in 1969 to complete a Grand Slam - winning all four major titles in the same year.
"The Grand Slam for Roger will be very tough," said Ivanisevic, 35. "I don't think he will win the French Open because Rafael Nadal is a better player on clay.
"If he stays healthy, Nadal can dominate the French Open for another five or six years.
"Nadal has had his difficulties this season but when the clay comes it is a different story. To beat Nadal on clay, I'd probably have to shoot him - and I don't know how to beat Federer either!
"There are only two guys who can beat Federer at the moment and that is Nadal on clay and Ivan Ljubicic on the hard courts and indoor.
"Ljubicic always gives Federer a tough battle with his huge serve but after he and Nadal nobody else comes close.
"Federer is the only player who can win the Grand Slam. He has a chance to become the best ever in the history of tennis - and for him anything is possible."