Australia batter Steve Smith was ruled out on the morning of the crucial third Ashes Test against England following symptoms of nausea and dizziness. Smith was replaced in the Australia line-up by Usman Khawaja.

The 36-year-old missed training on Monday because of illness, then was struck in the groin when he batted in the nets on Tuesday morning. A statement from Cricket Australia said: "Over the past few days he [Steve Smith] has been feeling unwell, with symptoms including nausea and dizziness. "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."

Smith was on the outfield at the Adelaide Oval before play began, only to leave the stadium before the toss took place.

"Steve has been feeling a little bit unwell over the past couple of days," said Australia captain Pat Cummins. "He gave it a crack this morning, but didn't think he was going to get up for this one. He's headed off home. "We're pretty lucky we've got someone like Usman who can step right in."

Khawaja, who was left out of the Australia XI when it was named on Tuesday, comes in to take Smith's place at number four. Australia, 2-0 up after wins in the first two Tests, will retain the Ashes if they avoid defeat in Adelaide. The hosts won the toss and chose to bat first.

Smith captained Australia to victory in the first two Tests in the absence of Cummins, who has returned to lead at the Adelaide Oval. It is a significant loss to Australia - only the great Sir Donald Bradman has made more runs for Australia in Ashes Tests.

Smith missed Australia's first Test against West Indies in June because of a broken finger, but this is the first home Test he has sat out since serving a ban for his role in the 'Sandpapergate' scandal in 2019.

It is a shock return for Khawaja, whose Test career looked over when he was omitted from the Australia team on Tuesday. The left-hander, who turns 39 on day two of the third Test, was unable to open in the first Test because of a back complaint - the same issue then ruled him out of the second Test. In his absence, Travis Head and Jake Weatherald have formed a promising opening partnership.

Khawaja batted at number four in the first innings of the first Test in Perth, moving down the order following the back spasms. The last time he was listed to bat in the middle order was the Sydney Ashes Test of 2022, when he made a century in each innings at number five.

Going on record to say the absence of a particular player is a boost to the opposition is fraught with danger. Still, if England could choose one Australian obstacle to remove in such a crucial Test, Smith would come pretty high on the wishlist. So often Smith has been the destroyer of English Ashes dreams. Run after run, hour after hour spent at the crease.

Conditions in Adelaide - a flat pitch, baking sun and Australia batting first - would have had Smith licking his lips. His absence also means a rivalry with Jofra Archer is put on hold. Archer bowled with rapid pace to Smith at the end of the Brisbane Test. Smith is always quick to point out that Archer has never dismissed him, even in that memorable spell on Archer's debut in 2019, when Smith was concussed by a blow to the head.

It is a remarkable return for Khawaja, who less than 24 hours ago looked to have come to the end of his Ashes career. He has a history of being called into Ashes matches in Australia. This really is a last opportunity to make a mark.