Usman Khawaja's fairytale comeback has presented Australia with a selection headache, and captain Pat Cummins conceded it would be hard to drop the in-form batsman from the fifth and final Ashes Test against England in Hobart next week.

Khawaja, 35, was picked to play his first test in 2-1/2 years only because Travis Head had tested positive for COVID-19, but he grabbed the opportunity with both hands, smashing a century in each innings and claiming the man-of-the-match award.

With a fit Head set to join the team in Hobart, left-hander Khawaja said he did not expect to be retained for the final Test. But Cummins did not want to rule him out.

"I'll preface it by saying I'm not a selector, but when someone comes out and hits twin hundreds, it's pretty hard to go past them for the week after," Cummins said after the drawn fourth Test at the Sydney Cricket Ground.

"So we'll work through that, the selectors will work through that in the next few days. But when someone's running hot, has got a heap of experience like Uzzy, the way he plays is fantastic."

Head's match-winning century in the opening Test had set the tone for Australia's dominance in the five-test series.

Considering Khawaja's ability to bat anywhere in the top order, Australia could also be tempted to play him as opener replacing Marcus Harris, who has managed only one half-century in the series so far.

Cummins said Khawaja's versatility made the batsman an asset to have.

"I guess that's why he was the spare batter and picked in the squad originally," Cummins said. "It felt like he could replace any batter one-to-six really well. He's hugely versatile."

"I know there's been question marks historically on him playing over in Asia, but you see how well he's played spin recently," he said, referring to the batsman's performance on the drier, spin-friendly wickets in Asia.

"Reverse sweeping, sweeping. He's just someone who is in total command of his game, and that's why you love experience."