Australia's ageing talisman Tim Cahill has endured a rocky road to his fourth World Cup but insists "given the chance, I'll always produce when it counts".

Cahill, 38, who has spent most of this season on the sidelines, will join exalted company if he can silence his doubters and find back of the net in Russia.

Only three other players have scored at four World Cups -- Brazilian legend Pele and the Germans Uwe Seeler and Miroslav Klose.

Cahill is the Socceroos' all-time top scorer, with 50 goals, and has 105 caps for Australia, a record for an outfield player.

"He's a special case," Australia's Dutch coach Bert van Marwijk said.

"He's special in everything. He's 38 and maybe one of the best-ever players for Australia. He's a very good striker."

In his pomp, Cahill carved up English Premier League defences for Everton and helped Australia reach the round of 16 at the 2006 World Cup.

He retains a knack for scoring crucial goals, including rescuing Australia's stuttering World Cup qualification campaign with a double against Syria late last year.

Yet Cahill's inclusion in the squad for Russia has proved controversial, stirring intense debate about a player previously seen as indispensible since his Socceroos' debut in 2004.

Cahill's doubters argue that his glory days are over and the veteran should make way for young talent.

After struggling for form with Melbourne City in the A-League, he departed for Millwall in February hoping to gain valuable game-time.

But he managed only 63 minutes in 10 substitute appearances for the London club, failing to score before picking up a three-match ban for violent conduct.

His spot in van Marwijk's 23-man squad announced on June 3 came at the expense of in-form Hibernian striker Jamie Maclaren, 24, who is not only match fit but scoring freely for the Scottish club.

There have even been suggestions Cahill was included for commercial reasons, rather than his football prowess.

The team's main sponsor, oil company Caltex, has based its World Cup advertising campaign around him -- branding itself "Cahilltex" for the tournament -- and his absence would see the costly marketing exercise fall flat.

"Absolutely not," Football Federation Australia David Gallop told reporters when quizzed about the issue.

"Have a look at Tim Cahill's track record. He's a guy who has produced for the Socceroos and Australia so many times... he's got a few weeks of intense training and he'll be right up there."

Despite advancing years and lack of form, there is little doubt that Cahill can once again be Australia's most potent threat if he rediscovers the class displayed through much of his career.

Born in Sydney to a Samoan mother and British father, he left Australia for London as a teenager in 1997 to join Millwall's academy after his parents went into debt to fund his footballing dream.

After reaching the 2004 FA Cup final with second-tier club, he joined Everton in 2005, making 256 appearances for the Toffees and scoring 68 goals over the next eight years.

Stints at New York Red Bulls and Shanghai Shenhua followed before he returned home to the A-League in 2016 in a much-hyped move to Melbourne that failed to meet expectations.

Over the years, the box-to-box midfielder has transformed into an outright striker while retaining his outstanding aerial ability.

Remarkably, more than half Cahill's international goals have come from headers, even though he stands only 1.78 metres (5ft 10in) tall.

A renowned fitness fanatic, he did double training sessions wearing monitors during his recent spell at Millwall and had the data sent to van Marwijk for analysis.

Cahill will feature as an impact player off the bench if, as expected, he makes van Marwijk's final squad.

With his vast experience, he has also adopted the role of elder statesman for Australia's playing group, most of whom have never played at a World Cup.

But he wants to go to Russia as a player, not a mentor, and says he is still capable of furthering Australia's cause by contributing on the field.

"I'm not naive enough to think I'm indispensible because no player is," he said.

"You can't... just think you can be there off romance or because you've done it before. You can't carry passengers when you go into such a big tournament."