MELBOURNE, July 26 AAP - Pat Rafter's easy-going personality will stop him being "consumed" by his newly-won No.1 world ranking, according to Neale Fraser, who topped the list almost 40 years ago.

Fraser headed the world's tennis players in 1960 when he won Wimbledon and the US Open - he was also the last Australian before Rafter to hold back-to-back US titles.

But Rafter, who today became the first Australian to take the No.1 mantle since John Newcombe 25 years ago, will be under intense pressure with a massive points defence looming in coming weeks.

"There's enormous pressure these days, far more than I had, because I think there's no really outstanding player, there's about half a dozen who probably all think that they should be No.1 and they'll all be vying for it," Fraser said.

"But his attitude is something that's going to hold him in good stead and his personality.

"I don't think it's the be all and end all for him, whereas for some others it might be the be.

"It's something that's not going to consume him a lot."

Rafter must defend points at Toronto and Cincinatti next month as well as at the US Open where he will be chasing a hat-trick of victories.

"I think he'll be feeling more pressure with the three tournaments in the American summer coming up because he had a fantastic summer last year and that's the reason why he's No.1," Fraser said.

"But being the No.1 he's going to be seeded high up and hopefully that will give him a slightly easier road in the touraments.

"It's most unusual for a player to win two Super Nines and a Grand Slam within the space of a month and Pat's got to defend those.

"But he's the type of fellow who's not going to think, 'if I go on court and lose this I'm going to lose my No.1 ranking', he won't do that."

Fraser agrees with many experienced observers that Rafter will become a better player.

"I think he's got to learn how to best get the best results out of his game. He has improved some aspects of his game, like his return of serve, markedly," he said.

"At the Davis Cup (win over the US) he didn't get enough first serves in on first points and if he learns to do those things and keeps in front of people and keeps them down he won't get behind so much.

"He's definitely got the ability to improve. He's physically strong and he's mentally tough and he's a nice fellow. He's got everything going for him."

At 26 years 7 months, Rafter is the fourth oldest man to be ranked No.1 for the first time, behind Newcombe (30 years 11 days), Austrian Thomas Muster (28 years 4 months) and Romanian Ilie Nastase (27 years 1 month).

Rafter is the fifth different No.1 this year, joining Pete Sampras, Carlos Moya, Yevgeny Kafelnikov and Andre Agassi but Sampras will regain the crown if he makes the final of this week's Los Angeles Open, which the Queenslander is not contesting.