Wallabies loosehead Scott Sio will undergo scans on his elbow after being injured in Sunday’s win over Scotland.
Sio twisted his arm in a scrum and finished his night in a sling and had limited movement on Monday morning, with a hematoma on his elbow.
The 24-year-old has been one of the crucial cogs in the Wallabies scrum so far in the tournament but the severity of the injury is yet to be known.
If Sio were to miss Australia’s semi-final, James Slipper would likely come into the starting side, with Toby Smith coming on to be the bench.
Australia’s scrum was put under pressure on Saturday night but Cheika said some of the side’s lapses in an emotion-laden win over Scotland were down to mindset.
“I’ve got to take a lot of responsibility for the team not filling its potential on Sunday,” he said.
“They were still thinking about the game against England and the game against Wales and I let that atmosphere stay.
“I should have just wiped those things out and just focused on the next challenge and just focused on the Scottish scrum or whatever it was in relation to the scrum.
“I’ll make sure that doesn’t happen again this week.”
After the match Cheika praised his side for sticking to its natural playing style and he reiterated that on Monday morning.
“We as an Australian team, we’ve got a certain identity that we want to play,” he said
“I know that when we threw the intercept last night it would have been easier to kick that ball away but if Drew Mitchell gets that ball, we’re away down the left edge, we’re gone and we can put the game away.
“We want to play that style of footy because we think it’s indicative (of that).
“Doesn’t have to be the way for anyone, that’s just our way.”
Cheika said the side was distinctly aware that they needed to step up for their semi-final.
“There’s no might, we will,” he said.
“You’ve got to pick up, got to improve.
“I think that without improvements we won’t get the outcome we want. That’s honest.”
In positive news for the Wallabies, Cheika is optimistic about the chances of David Pocock and Israel Folau returning for Sunday’s semi-final.
The Wallabies missed Pocock at the breakdown against Scotland but Cheika said the number eight had run pain-free on Sunday and was confident around Folau’s chances as well.
Australia plays Argentina for a spot in the World Cup final on Monday October 26 3am AEDT.