Head coach Lehmann's side trail 2-0 in the Investec series after defeats at Trent Bridge and Lord's, meaning England can retain the urn and win the series when the sides reconvene at Old Trafford on August 1.
The problems facing the tourists are considerable, starting with the limp performances of the top-order batsmen but extending to their consistently muddled use of DRS and a number of off-field issues that are threatening to overshadow the main job of playing cricket.
One three-day match against Sussex at Hove, starting on Friday, might not be enough for them to get everything back on track but it is the best chance Australia have.
Captain Michael Clarke made no attempt to hide the fact that the Baggy Greens are struggling when assessing the overwhelming 347-run defeat at the home of cricket and Lehmann is singing from the same hymn sheet.
He has already used 13 of his 18-man squad in the first two Tests and pledged to give at least two more - reserve wicketkeeper Matthew Wade and spinner Nathan Lyon - the chance to impress against Sussex.
The likes of Jackson Bird, James Faulkner and David Warner - the bad boy batsman who will return from Australia A duty in time for the third Test - have also been told they could be needed as the selectors scramble for a winning formula.
"I say all the time the whole 18 have a chance to play," said Lehmann. "I'm not ruling anything out. That is what happens when you have two losses, every option is open.
"As selectors Rod (Marsh), John (Inverarity) and I will have to speak about it and see where we come to.
"Ashton (Agar) is a bit sore and I don't think he will play in Sussex so Nathan Lyon will play obviously. Then we just have to look at the wicket (at Old Trafford) because history shows it spins a bit.
"If it's going to spin we will certainly have a look at two spinners. Wade will play in the tour match too."
England have already banked three centuries in the series, two to Ian Bell and a maiden Ashes hundred to Joe Root, but Australia's batsmen have proved far too flimsy.
Indeed, the closest they have come to an Ashes ton was the 98 Agar scored from number 11 at Trent Bridge and few of the top seven have looked likely to better that.
"We have certainly got to bat better, we know that," admitted Lehmann. "It's probably more of a mental thing. We need to make sure we're ready to go...have a good time down in Sussex, play some decent cricket and bat a lot longer than 90 overs.
"We had two guys get to 50 at Lord's but 50 isn't going to get us to where we need to go. Clarke and (Usman) Khawaja batted really well but they need to make hundreds when they get to that position, just like young Root did.
"We have certainly had poor shot selection for a start, but (England) have bowled quite well, give them credit. We have to get better at facing reverse swing, off spin, all those sorts of things that make you bat for long periods of time."
Lehmann, a dyed-in-the-wool cricket man if ever there was one, is not interested in wading into the off-field affairs circling his squad - a sorry looking list that includes inter-squad personality clashes, Twitter storms and the ongoing legal claim from his predecessor Mickey Arthur.
"We actually need to get some results because that would stop all the talk and make people realise we are going the right way," he said.
"We can't worry about what anyone else says or writes. We accept the criticism, we deserve the criticism to be fair. But we've got to make sure we're going in the right direction, so those sorts of things I just brush off."