ADELAIDE, Australia, Dec 17, 2025 (BSS/AFP) - Australia's Steve Smith was ruled out of the third Ashes Test against England just before it started Wednesday, in a big setback for the hosts, with the batting kingpin replaced by Usman Khawaja.

Smith, who captained the team in Perth and Brisbane, missed training on Monday with illness but batted on Tuesday and was initially named in the starting XI.

"Steve's feeling a little bit unwell the last couple of days," said returning skipper Pat Cummins.

"He came in and gave it a crack this morning, but didn't feel like he could get up. He's headed off home.

"Pretty lucky we've got someone like Uzzie (Khawaja) who can step right in. Uzzie bats at four."

Smith has long been Australia's middle-order rock, a player with 36 Test centuries and more than 10,000 runs and his absence is a huge blow.

He was on the field Wednesday but was seen walking off 20 minutes before the toss after a chat with coach Andrew McDonald.

It handed a lifeline to 85-Test veteran Khawaja, who had been axed as opener with selectors opting to stick with Travis Head and Jake Weatherald.

It capped a dramatic build-up to the third Test in which Australia is chasing an unassailable 3-0 series lead and England battling to keep the Ashes alive.