The Victorian was flown to Brisbane and put on standby for both Marsh and opener David Warner, who was still receiving treatment for discomfort in his neck.

Marsh was seen speaking to Australian team physiotherapist David Beakley after batting in the nets in the final pre-Test hitout, and it later emerged he had reported an issue with his back.

Selectors convened immediately after Australian training and decided to have Maxwell join the squad in Brisbane later in the day.

The Victorian was dumped from the Test side only last Friday as the panel opted to go without an all-rounder at No.6 and instead plonk a recalled Marsh into the middle order.

While the hosts are confident Warner will be fit to play, the doubt over Marsh means Maxwell could be rushed into the line-up for his first Test in Australia, replacing the player who was preferred over him by Trevor Hohns' panel.

Maxwell was technically brought in as cover for both Warner and Marsh, but the fact Australia chose not to add a second back-up batsman to the squad reinforced a belief that only one of them was in genuine doubt.

That appeared to be Marsh, whose stop-start, 23-Test career has been interrupted previously by injuries.

Given his history, Australia would have to be cautious about taking him into an Ashes match, even with a minor complaint. He broke down during his last Test, against India in Dharamsala, and subsequently lost his Cricket Australia contract and was overlooked for the Test tour of Bangladesh in the spring.

Maxwell has played in Australia's previous four Tests, scoring a maiden hundred in India this year, but despite two half-centuries and an unbeaten 45 in six innings he was told by selectors last week that he had not done enough in three rounds of the Sheffield Shield this season to warrant retention.

Marsh, 34, was instead given the nod, recalled to the Australian team for the eighth time since making his Test debut in 2011.

Despite having a heat pack applied to his neck on Wednesday, there was confidence in the Australian camp that Warner would take his place in the line-up. The vice-captain spent a lengthy period batting in the nets, having balls thrown at him by CA spin bowling coach John Davidson.

Warner's withdrawal would be a huge blow for Australia and a leveller of sorts, with England here without their most complete player, Ben Stokes, as he awaits the outcome of a police investigation into a fight outside a Bristol nightclub in September.

"Davey's going well," Smith said. "He just had a hit just before, he is very confident. He says he'll be right to go.

"It's part and parcel of cricket. Guys have injuries every now and again and have little niggles, but we are confident that he will be OK. He said he will bat like Shivnarine Chanderpaul if he has to and face the other way, but I think he will be all right."

Warner picked up the injury during a fielding drill on Tuesday and Smith said it was in moving his head back that his deputy was feeling pain.

"I think he has improved the last 24 hours, and hopefully he can keep improving and be 100 per cent at 10am tomorrow morning," he said.

England XI: Alastair Cook, Mark Stoneman, James Vince, Joe Root (capt), Dawid Malan, Moeen Ali, Jonny Bairstow, Chris Woakes, Jake Ball, Stuart Broad, Jimmy Anderson