In what is becoming a regular occurrence, the Australians folded spectacularly losing eight wickets for 32 runs in just under 20 overs for an innings and 80-run defeat to the Proteas before lunch on the fourth day.
The batting freefall has intensified scrutiny on Steve Smith's embattled side after their fifth straight heavy Test defeat this year, all by 100 runs or more.
Lehmann, whose coaching position is also under scrutiny after it was extended to 2019 only last August, said there will “definitely” be changes for next week's final day-night Test in Adelaide.
As a consequence of the early-finishing Hobart Test, all batsmen, including wicketkeeper Peter Nevill and spinner Nathan Lyon, but not the three pace bowlers, will be required to play in this week's round of domestic Sheffield Shield before the Test squad is named on Sunday.
Lehmann, who also sits on the selection panel, said that only Smith, David Warner and pace pair Mitchell Starc and Josh Hazlewood would be sure of keeping their spots.
“We've got to stop the rot, we've got to work out what the best XI is,” Lehmann told reporters.
“Guys playing in this Test match, some were disappointed in their performances and they get the chance to play the Shield games to put their hand up.
“I thought Hazlewood was great, Starc's getting back to his best and then you've got Smith and Warner.
“Outside of that everyone's got to make some runs and take some wickets. It's a really important four days of Shield cricket.”
Those looking down the gun are 37-year-old batsman Adam Voges, opener Joe Burns and Callum Ferguson, who both came in for the Hobart Test. Spinner Lyon is another whose place is at risk after taking just two wickets at 120.50 each in the South Africa series.
“Like everyone else, Adam's been a very good player for us for 20-odd Test matches. End of the day he's got to go back and make runs like everyone else,” Lehmann said.
The coach said there was a desolate mood in the dressing room after the defeat.
“Everybody is hurting in the rooms. I haven't seen it as quiet after a loss and that's understandable because of the performances,” he said.
“We pride ourselves on playing for our country and we haven't done that well enough over the last three and a half days.”
He said former greats were talking with the shattered players, offering advice and support going forward.
“Mark Taylor and Shane Warne have been chatting to the guys one on one. Ian Healy, Tom Moody, Simon Katich, Brett Lee, we've had a lot of the legends come in,” he said.
“The young guys who are playing today looked up to them. It's great to have them in the rooms and speaking to them.”
Original source: Only four safe in shattered Australia - Lehmann