Uncapped Australian batsman Usman Khawaja has been brought into the squad for this week's first Ashes test after vice captain Michael Clarke failed to train because of a bad back on Monday.
Top order batsman Clarke suffered a recurrence of a long-term lower back problem in a recent Sheffield Shield match and failed to suit up for training in Brisbane, where the first test against England begins on Thursday.
"Didn't train today, back a little stiff," he posted on his Twitter page.
"Confident if I keep listening to our physio and doing the right things I will be fit for thurs."
Free-scoring Khawaja was in the original 17-strong squad for the test but dropped when it was reduced to 13 on Saturday after he failed to impress for Australia A against England in Hobart.
"As there is some doubt over Michael Clarke's fitness for the Brisbane test match, it was felt prudent to bring a standby player into the squad," chairman of selectors Andrew Hilditch said in a news release.
"We intend to give Michael as much time as possible to prove his fitness and a decision on his availability will be made in consultation with the team's medical staff after the next two days of training," he added.
Team physiotherapist Alex Kountouris said Clarke was making good progress and was expected to train on Tuesday and Wednesday.
There was more bad news for Australia, however, when Tim Paine, the back-up to wicketkeeper Brad Haddin, was discovered to have broken a finger in a Twenty20 match in Brisbane on Sunday night.