Australia face a nervous wait ahead of the first Ashes Test in Brisbane, with vice-captain and middle-order lynchpin Michael Clarke in doubt with a persistent back injury.

Concerns over Clarke’s fitness heightened after he took little part in Australia’s first training session ahead of this week’s opening Test.

While the rest of Australia’s 13-man squad were equipped with their batting and training gear on arrival on Brisbane’s Allan Border Field, Clarke walked out without his kit.

He also played no part in the squad’s warm-up, instead just walking around the oval.

Clarke has been plagued by a chronic back injury for much of his Test career and aggravated it while scoring a Sheffield century for NSW a fortnight agao.

“I’m still a little bit stiff and sore, hence me not training today,” Clarke said. “Our plan was for me to have a bat tomorrow and then another good hit on Wednesday. The battle is to get as close to a hundred per cent as possible for Thursday. I’m pretty confident that I’ll be right.

“I’ve played international cricket with discomfort because of my back, but it hasn’t ruled me out of a Test match as of yet.”

All-rounder Steve Smith, the only other batsmen named in the 13-man squad, would have been the logical replacement for Michael Clarke but the Australian selectors have kept their options open by bringing in 23-year-old batsman Usman Khawaja as cover.