In a major departure from his usual routine, Steven Smith did not appear for a habitual net at Australia's main training session prior to the first Test against India in Adelaide.

The only sight of Smith for the afternoon was in early warm-ups and fielding, but around 10 minutes into the session he gestured to support staff and headed for the dressing rooms, shaking his left arm as he went.

While the Australian camp played down the issue, Smith did not reappear for a nets session that featured plenty of close attention paid to Joe Burns by the coach and selector Justin Langer.

An Australian team spokesman would say only that Smith had a sore back that was getting a rubdown later adding that he would train on match eve, after tweaking his back when bending down to pick up a ball.

Smith's non-appearance added another layer of mystery to Australia's already chaotic preparation for the series following a litany of injury, conpassionate leave and misadventure that has so far included David Warner (groin), Will Pucovski (concussion), Mitchell Starc (personal leave), Cameron Green (concussion) and even his nominal replacement Moises Henriques (hamstring).

Burns faced just one ball, played to the leg side, before he received the first of a couple of mid-pitch pep talks from Langer, who later walked to the back of the nets to observe the opener from behind the stumps.

Parallel net sessions from the captain Tim Paine and fellow batting aspirant Marcus Harris attracted relatively scant attention from Langer, who clearly wanted to give Burns support whenever he hit one cleanly in an extended stint against James Pattinson and Michael Neser.

At the same time, the likely debutant Green continued his steady progress back from a mild concussion in the SCG warm-up game against Virat Kohli's tourists, bowling at a leisurely pace and then batting against throwdowns and spin.

Green's pathway to playing is clear, so long as he keeps up his improvement in terms of the steps required by Cricket Australia medical staff and their concussion protocols.