Australian tennis legend Rod Laver has urged countryman Bernard Tomic to stay true to his unconventional style.

But the only man to win two calendar grand slams has also warned Tomic - who turned 21 this week only to withdraw midway through a match the following day reportedly suffering from a headache - that he can't pick and choose when to play at his best.

Tomic remains the youngest man in the top 80 of the world rankings, although his current ranking of 52 is something of a disappointment having started the year on a high by winning the Sydney International.

Laver was on hand at the All-England Club this year as Tomic produced his best grand slam effort of 2013 - reaching the fourth round at Wimbledon before bowing out to world No.6 Tomas Berdych.

"I thought he played some great tennis - he's very, very capable," Laver said on Thursday at the launch of his biography, appropriately held at Rod Laver Arena.

"He's got a different game and that's why a lot of people feel that he might not be playing up to his best standard.

"But that's the way he plays the game, so I don't think people should get too critical of why perhaps he tried a drop shot if he misses it.

"He's doing it for a purpose.

"Some of the things don't pan out but when he played a guy called Richard Gasquet at Wimbledon he actually made him look (silly).

"The way he was playing with him, he was playing drop shots, he was playing slow shots, easy shots, serving aces, that's the way he plays.

"Tomic is putting opponents off with the way he plays, so I hope he doesn't give that up."

The Queenslander also won plaudits for his role in getting Australia back into the Davis Cup World Group after an absence of seven years.

But the flipside was on show in Valencia this week, when Tomic pulled out in the deciding set of his first-round clash with Russian Mikhail Youzhny.

"I know there are some down times and when he looks back at things in five or 10 years he may be disappointed with himself," said Laver.

"If you don't put your best effort in every time you won't know when the best time is to play your best tennis.

"It doesn't just gel when you think `OK I'm going to play good today'."