Smith ruled out on the morning of Adelaide with vertigo, Khawaja recalled

Steven Smith has been ruled out of the third Ashes Test on the morning of the match in extraordinary circumstances with Usman Khawaja earning a recall just a day after it seemed unlikely that he would play another Test for Australia.

Cricket Australia (CA) confirmed just before the start of play that Smith was suffering vertigo type symptoms, something he has battled with in the past. He left the ground during the warm-up after he had batted in the nets and had a conversation with coach and selector Andrew McDonald.

Smith missed training on Monday due to illness but had trained on Sunday at Adelaide and then played golf with his team-mates at Kooyonga on Sunday afternoon.

He returned to training on Tuesday and was first in the nets. But he did not look in full health during the net session and was also hit in the groin at one point which felled him and caused him to take a lengthy break.

"Over the past few days he has been feeling unwell, with symptoms including nausea and dizziness," a CA spokesperson said.

"He was assessed and monitored closely and was close to being available to play. However, given the persistence of symptoms, a decision was made not to proceed.

"He is being treated for a potential vestibular issue. This is something Steve has experienced intermittently in the past and is being managed accordingly. He is expected to be available for the Boxing Day test in Melbourne."

Pat Cummins, who returned as captain after Smith had led the first two Tests, confirmed after winning the toss that Khawaja would replace him.

"Steve's been feeling a bit unwell the last couple of days," Cummins said. "He came and gave it a crack this morning but didn't think he was going to get up for this one. So he's headed off home. But pretty lucky we've got someone like Usman who can step right in. Usman will bat No. 4"

Khawaja has been recalled after Australia had elected to leave him out despite returning to full fitness from a back injury, with the success of the Travis Head-Jake Weatherald opening partnership in the first two Tests forcing the selectors' hand. Even with Khawaja's last-minute return, the selectors have decided to keep Head and Weatherald at the top. Khawaja will slot in at No. 4 with the rest of the order remaining the same.

Khawaja has only twice batted at No. 4 in Test cricket, including in the first innings of the first Test in Perth when he was unable to open due to back spasms. It has been his preferred spot to bat in first-class cricket, averaging 53.15 with 10 centuries. He batted at No .4 in Sheffield Shield cricket for Queensland for several years while he was Australia's Test opener.

Khawaja will turn 39 on Thursday, and become the first 39-year-old to play for Australia in 40 years.

Smith has missed two of Australia's last six Tests through injury or illness. He missed Australia's first Test of the West Indies tour in June due to a finger injury he suffered in the WTC final. Josh Inglis batted at No. 4 on that occasion.

Prior to that he had not missed a Test since the third Test of the 2019 Ashes series when he was ruled out with concussion. He has suffered several bouts of vertigo in the intervening years but none that have kept him out of a Test match.