Phil Kearns backs Bernard Foley over Christian Lealiifano as Australia's No. 10

Former Wallabies captain Phil Kearns believes Bernard Foley shades Christian Lealiifano as the ideal Australian five-eighth at the Rugby World Cup and hopes a way can be found to restore the "Pooper" back row mix.

Kearns leaned towards what worked best at the 2015 tournament when assessing the tight selection calls coach Michael Cheika will have to make in Japan.

Foley was one of the tournament's best players as the Wallabies marched to the final at Twickenham four years ago, although some critics say he hasn't played as well since.

Lealiifano is seen as having his nose in front in the battle to wear No. 10 against Fiji in next week's opening pool game.

Boasting superior Super Rugby form than Foley, in a Brumbies team playing at a higher level than the Waratahs, Lealiifano ended three years out of the test scene with starts against Argentina and in both Bledisloe Cup showdowns.

He added a fluent dimension in the 47-26 win over the All Blacks in Perth but was guilty of basic errors in the following week's return 36-0 loss at Eden Park.

"It's great to have Christian back. He showed a really good performance but also an average performance," Kearns told AAP.

"When Bernard's on song, he's a very, very good 10 and very reliable, which is so important.

"I think the biggest issue isn't so much which one but who can be most consistently good?

"And I think your 10 is probably going to have to be playing six games or seven games at the tournament, so that consistency factor is critical."

Foley, who turned 30 on Sunday, wasn't at his best in general play and with his goal kicking in the previous day's 34-17 win over Samoa.

Cheika gave no hint of his preference for the playmaking role, saying "maybe there isn't a wrong choice" in several of his squad's most competitive positions.

Pocock shone on return from injury against the Samoans and Kearns wants to see him back in tandem with captain Michael Hooper, giving the Wallabies two world class breakdown exponents.

His biggest concern is whether Australia have an ideal third back-rower to complement them.

The other candidates are impressive rookie No.8 Isi Naisarani, the versatile Jack Dempsey or powerhouse blindside flanker Lukhan Salakaia-Loto, who has played every minute of all five tests this year.

"When you're talking about the best sixes and sevens in the world, Hooper and Pocock would get a mention," Kearns said.

"The work rate's phenomenal but if you've got those two, you need a tall back-rower as well and perhaps that's where we're lacking."

AAP