While the name Tim Cahill is now synonymous with football in Australia, the nation's all-time leading goal scorer says he wasn't predicted to reach such heights.

"I was the smallest in my team and I tried my hardest ... and I got overlooked," he said.

Born in western Sydney, Cahill, whose career began with games for Lakemba Sports Club, Balmain Police Boys Club and Marrickville Football Club, said he was told that he was too small to ever be a professional footballer.

Now, the retired great has launched his 10th children's book in the Tiny Timmy series, which follows the adventures of a small soccer player who struggles to make team selection because of his size.

It's a battle 11-year-old Raph Merchant King knows all too well.

"My dream growing up is to play soccer," Raph told Cahill on ABC Radio Sydney's Breakfast program.

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Now a midfielder for the University of Sydney Football Club, Raph has been playing the game since he was five.

He, too, has been told he won't make it into a top-ranked team because of his size.

"For a small player like me who's playing a high level of football, what would you ask me to always remember in a game?" he asked Cahill.

"Little man, that's so inspiring," Cahill responded. "For me, what I would ask you to always remember is to do the basics well.

"Even my last World Cup and all of the biggest games I've ever played in, one of the biggest things I do when I go on a pitch in front of a big crowd is I control the ball really well and make the pass really simple.

"I don't overcomplicate things, and as the game goes on, as I build confidence, I do more and then I feel like I get myself into my game."

Cahill said he planned on devoting his future career to inspiring players like Raph — and would consider naming a book character after the young Sydney fan.