Just six days after the one of the most courageous and gutsy defensive efforts in Wallabies history - and boasting a side that has leaked just two tries in the tournament - Grey wants the players to rise to a new tackling level in a World Cup quarter final.

The Wallabies are still nursing some battered bodies after their superb tackling display against Wales last weekend, where they somehow survived seven minutes with just 13 players on the field.

Experts have lauded it as one of the greatest defensive performances of any Australian team as they held up Wales across the try-line four times and refused to wilt under pressure.

But Scotland pose a new threat and Grey says anyone still replaying the effort against Wales will be caught out by a Scotland team capable of scoring from anywhere.

"It's not so much freshening them up. The guys are very good mentally," defence coach Grey said.

There is a real clear understanding that we will need a better defensive effort going into the knockout stages of the tournament that we're in.

"The guys have been training really well and we need to keep improving in each session."

It's hard to imagine a better defensive performance than that the Wallabies produced against Wales.

Australia may have leaked just two tries, but Scotland have shown their attacking potency, scoring 14 tries in their four games.

That leaves them three behind the Wallabies' try-scoring tally, but Australia also had an 11-tries-to-nil rout against Uruguay.

In overall points, Scotland (136) is just five behind the Wallabies (141).

"Yeah for sure [we can defend better]. We still leaked points … six [against Wales] is too many as far as I'm concerned," Grey said.

"We're always searching for things that we can continually improve. The penalties we gave away are things we can control and we should've not been able to do that.

"The guys are under no illusion around we've got to continue to improve … we'll take confidence out of performances we've had and that will set us up for our biggest game of the year."

The Wallabies will name their team on Friday (Friday night AEDT) with coach Michael Cheika sweating on the fitness of injured duo Israel Folau and David Pocock.

Folau is expected to be ready to take his place at fullback after nursing an ankle injury for the past two weeks while Pocock is being given as long as possible to recovery from a calf injury.

Matt Giteau, who will play his 100th Test, has ticked all the boxes in his recovery from a concussion and has shown no lingering symptoms in his return to training.

Kurtley Beale and Ben McCalman loom as the men most likely to fill any holes if Folau and Pocock are unable to take their places, while vice-captain Michael Hooper is expected to make his comeback from suspension at openside flanker.

WORLD CUP QUARTER FINAL

Wallabies v Scotland at Twickenham, Sunday 4pm (Monday 2am AEDT).