Fast bowler Joe Mennie is almost certain to make his Test debut in Hobart after Peter Siddle was ruled out due to a back injury.
Australia's selectors have also called on Jackson Bird as cover for the bowling unit but he is not officially part of the squad, which means Mennie is set to join Josh Hazlewood and Mitchell Starc in the pace attack for the second Test against South Africa, starting on Saturday. Mennie was named 12th man for the WACA Test and was then released to play a Sheffield Shield match for South Australia.
Siddle was preferred in Perth, where he was making his return to international cricket following a lay-off due to a stress fracture of the back, diagnosed following Australia's Test tour of New Zealand earlier this year. Australia's medical staff are hopeful that Siddle will recover quickly, but have taken a cautious approach due to his recent history.
"Peter Siddle had some lower back soreness at the conclusion of the first Test match in Perth," Australia's team physio David Beakley said. "Whilst we expect bowlers to be sore after Test matches, this was slightly worse than we expected and given that he was returning from a significant back injury, we organised some scans today.
"The scans demonstrated some low grade bone oedema around his old stress fracture that is likely to be a flare-up of his previous lower back injury. We are hopeful that this will resolve relatively quickly, but have withdrawn him from the squad for the second Test match in Hobart. We will monitor his recovery and have a better idea of when he will return to play in the next week or so."
Siddle's injury is yet another consequence to be drawn from Australia's horrid batting collapse on day two of the WACA Test, sending Australia's bowlers - Siddle and Starc with limited preparations - back into the field only 24 hours after they had bowled the Proteas out on day one. The coach Darren Lehmann said back-to-back Tests would stretch his men physically after they were made to work hard by JP Duminy and Dean Elgar in particular.
"They have bowled four days in a row," Lehmann said. "They are pretty sore as I would imagine the South African boys would be, the two bowlers that bowled the whole game for them. All bowlers are going to be pretty sore and tight. We'll just have to see how they pull up and make a call from there. They will have the same issues.
"It's a short turn-around. That's the nature of cricket in Australia, back-to-back Test matches early on. The good thing, I thought we batted a lot better in the second innings. The disappointing thing is we were off to flyer, obviously 0 for 158, and we lost 10 for 86. That's the thing that hurts you in a game, as you know. If we had the discipline and that in the first innings that we showed probably yesterday and today, we would have made a better score and a better fist of it in the first innings and had a lead.
"That's the challenge, isn't it? First innings, they made us pay in the second, Duminy and Elgar batted really well. I thought our bowlers worked hard the whole game and then coming in, if we had batters in in the last session today, well, you never know, do you? We just lost batters at the wrong time."
Asked about Australia's limited preparation, one Sheffield Shield match, and moving the first Test of summer from Brisbane to Perth, Lehmann said his hands were tied: "Can't do anything about it. Love to, but we can't."
The selectors had already added Callum Ferguson and Joe Burns to the Test squad to replace the injured Shaun Marsh (broken finger) and also provide cover for Adam Voges (hamstring). Lehmann confirmed both batsmen would be under consideration even if Voges is passed fit, placing further pressure on the underperforming Mitchell Marsh.
"We have known about the broken finger for about three days, which has been very good from our boys not to get out to you guys," Lehmann said. "We have known the squad is going to be changed in the last three days. I would say every spot is under pressure. That's the nature of the beast if you don't have success. I thought he batted quite well and was a bit unlucky with the decision, but that is part of the game as well."
Lehmann acknowledged that the national team were under a rare level of pressure, as four consecutive Test match losses have historically led to a change of the Australian captain or coach. "[We'll] Try to clear their minds," he said of the players. "But everyone has pressure. Everyone has pressure when not playing well. But also as a player you always have pressure to perform at international level.
"If you have a few bad performances, there is always someone waiting in the wings. And that's been the case for 100 years, that's not going to change I wouldn't think. We try and pick and stick where we possibly can and encourage the guys and we get in trouble when we don't pick and stick, we get in trouble when do pick and stick with you guys. So then when we add someone, it all changes.
"So, there is pressure on players day in, day out for your country and that's part and parcel of whether you are playing for South Africa or Australia."

Daniel Brettig is an assistant editor at ESPNcricinfo. @danbrettig