Hip damage to Jamie Robinson and Sonny Parker has forced coach Gareth Jenkins to reschedule his training programme as the tourists seek to avenge their agonising 29-23 defeat in Sydney last weekend.
The injuries could also delay the team announcement for the Suncorp Stadium clash by 24 hours to Thursday with Thomas on notice to move from right wing to centre.
Jenkins said: "There are a couple of injuries around after a physical game and we are not actually clear as to where we are with them.
"We've moved our training towards the end of the week when our plan had been to train Monday afternoon, Tuesday and have a day off on Wednesday.
"Well, we've changed that and cancelled training on Monday and we'll take a rest day on Tuesday, then train Wednesday, Thursday and Friday.
"That's the best we can actually do at the moment because of the injuries and we'll probably name the team on Thursday.
"Sonny Parker and Jamie Robinson have injuries around their hips. They have both taken knocks that are severely bruised.
"Gareth can play 11, 12, 14 or 15 and it's good to have that option if we need it and going to the World Cup with only 30 players you need the sort of players who can cover a number of different positions."
Wales will be looking for a general improvement across all areas and forwards coach Robin McBryde says working on deficiencies at line-outs and scrums will be top priority.
McBryde said: "The line-out was a disappointment to us. We had limited quality ball from there and there were also problems with our scrum.
"There were too many small things missing that developed into big things and that was it - a mixture of errors on our behalf and that's not to take anything away from the strength of the Australian line-out.
"But we were guilty of making some basic errors as well."