Steve Smith has launched an impassioned defence of the out-of-form Cameron Green, but cannot guarantee the all-rounder's place in Australia's XI for the final Ashes Test.

Smith, Australia's stand-in captain, insisted all options were on the selection table for the fifth Test against England at the SCG, which begins on Sunday.

These options include using both all-rounders, Green and Beau Webster, and leaving out a spinner for the third time in four Tests.

"We'll figure [the team] out once we see the surface and see which way we want to go about it," Smith said.

With the Ashes urn already retained, World Test Championship points and the chance to send retiring Usman Khawaja out a winner appear the hosts' most significant motivations.

But pressure is mounting on 26-year-old Green, the youngest member of the team.

A solid contributor with the ball this Ashes series, Green has shifted around the batting order with an average of 18.7 runs and one score above 24 from six innings.

Even that high score — 45 under lights in Brisbane — was overshadowed by an audacious premeditated shot that left his stumps exposed and he was skittled by Brydon Carse.

Smith, who endured a lean start to the last home summer, felt for Green.

"We've played on some hard surfaces for batting," Smith said.

"We've seen two two-day games. It's not easy, but he's got himself in on a few occasions and probably not gone on with it.

"That's probably the disappointing part about it — starting your innings is actually the hardest thing. He's doing that pretty well and just finding a way to get out.

"He's batted in different spots, which also can't be easy, as well, when you're trying to nail down one sort of role."

Spinner Todd Murphy's hopes of a first home Test are also up in the air after he was overlooked for the seaming MCG deck.

Murphy last played on the Test tour of Sri Lanka in early 2025 and was brought into the Ashes squad as cover for injured veteran Nathan Lyon.

AAP