Lionel Messi could have been playing for Australia against Argentina in World Cup

Australia are Lionel Messi and Argentina's opponents in the World Cup round of 16 on Saturday but a shock report claims the seven-time Ballon d'Or winner could have been lining up on the opposite side.

But things could have been very, very different. According to journalist Guillem Balague, who wrote the book 'Messi: The Definitive Biography', the 35-year-old was almost a 'Socceroo'.

It's said that during the 1980's, where Argentina were in economic crisis, the Messi family were considering moving Down Under.

It was a genuine though that crossed the mind of Messi's dad Jorge, though he decided to remain in Rosario and on 24 June 1987, Messi, arguably the best player in history was born.

The clan, which include Messi's mother Celia Cuccittini and three siblings, relocated to Barcelona in 2001 when he signed a contract after a successful trial.

"It must have been a casual conversation that [father] Jorge Messi had before Leo was born that he had with somebody that came across with the idea of going to Australia to live. Why not?

"When you get in that mind frame in which the solution to your problems is to be abroad, it doesn't really matter where you go. And they knew people that had come to Australia.

"Finally, the decision was to stay put. Leo was born. When he's 12, he eventually gets a trial to Barcelona."

There's no guarantee that Messi, who suffered from growth hormone deficiency, would have made the grade in Australia given the popularity of sports such as NRL, AFL and rugby union in the country.

Messi was also eligible of playing for Italy through his great grandfather who emigrated from Recanati to Rosario.

And Messi has revealed that Spain were desperate to try and get him to play for them after he joined Barcelona, though he had his heart set on representing his country of birth.

"I was asked informally if I wanted to play for Spain, but I always said that I wanted to play for my national team because I love Argentina and these are the only colours I want to wear," he said in Messi, The Patriot.

“I was always an avid fan of the national team. I watched the games on television because I could never go to the grounds and watch them as a fan."