The young gun and the old head: Adam Ashley-Cooper set for mentoring role at World Cup

Adam Ashley-Cooper has been described as a perfect mentor for the likes of boom midfield back Jordan Petaia, with Michael Cheika confident he has an ideal blend of Wallabies to contest the Rugby World Cup.

Midfield backs Ashley-Cooper and Petaia - the oldest and youngest players to feature in any Australian World Cup squad - captured most attention when Cheika unveiled his 31-man group in Sydney on Friday.

Boasting an Australian tournament-record 45 caps per player, Cheika's Test-hardened group features three centurions in Ashley-Cooper, halfback Will Genia and prop Sekope Kepu. Two others poised to raise three figures in Japan are captain Michael Hooper and lock Rob Simmons.

Ashley-Cooper, 35, is the most venerable and had been widely regarded as a long shot at joining George Gregan as the only four-time World Cup Wallabies.

Cheika revealed the 118-Test veteran was selected because he shaped as a perfect sounding board for uncapped 19-year-old Petaia and more than half the squad who will be making their global tournament debut.

"If you look at the composition of the squad, 18 have never been to a World Cup," Cheika said.

"We'll definitely be looking at those other 13 to have an impact. That little bit of extra experience makes younger players who haven't been there feel comfortable enough to express themselves and go for it.

"Players like Ashley-Cooper help that happen. I'm big on the complementary nature of teams."

Cheika said Petaia had been on his radar for 18 months and the gifted Queensland attacker came close to earning a first Test cap last year.

The teenager suffered a serious foot injury in early March and has needed recent club rugby to prove his fitness.

Twelve of the squad were involved in the 2015 campaign when Australia defied the odds by reaching the final at Twickenham, where they lost to the All Blacks. Seven of those players were also at the 2011 tournament.

A born-again James O'Connor attended 2011 but missed 2015.

O'Connor is among a jam of midfield backs announced by Cheika. Nine of his squad have started a Test at inside or outside centre and Petaia is poised to become the 10th.

He has also named a full complement of three hookers and four locks, leaving other positions thin on numbers.

There are just two halfbacks - Will Genia and Nic White - with Cheika unwilling to reveal who else could be converted as cover for the specialist role.

Among just five loose forwards is veteran David Pocock who hasn't played since March because of injury.

Notable absentees include fullback Tom Banks, halfback Joe Powell, hooker Tatafu Polota-Nau and flankers Liam Wright and Luke Jones, who will work with the squad as train-on players at a 10-day preparation camp in New Caledonia.

Cheika described phone calls to omitted players as "emotional" but praised their willingness to contribute.

"You feel guilty for leaving them out but you're so excited and proud that your players will give you everything, even when you deliver them news that will really affect them."

The Wallabies have a final hitout against Samoa in Sydney on September 7, two weeks out from their opening group game against Fiji in Sapporo. The other pool opponents are Wales, Uruguay and Georgia.

AAP

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