London - Leading England out of their Ashes slump will be the biggest challenge of captain Alastair Cook's career, according to former skipper Nasser Hussain.
After three series successes, England relinquished their grip on the urn on Tuesday when Australia recorded a third consecutive Test victory in Perth to establish an unassailable 3-0 lead in the five-match series.
With Tests in Melbourne and Sydney still to come, England are at risk of a humiliating series whitewash, and Hussain wants Cook to stand up and be counted.
"This is now the hardest time of his career," Hussain told Sky Sports.
"Three-nil down, Australians want 5-0, his game is struggling, he's got bowlers all over him like a rash, he's got an opposition captain (Michael Clarke) that is out-captaining him.
"He's often in the past come back in these situations. This will be the toughest for him."
Another former England captain, Michael Atherton, has urged Cook to view the situation as a chance to rebuild the team that he inherited from predecessor Andrew Strauss.
"Alastair Cook can look at this as a fantastic opportunity," Atherton said.
"He basically inherited Andrew's side, a very good side, but it's clear that this side is coming to the end of its time.
"How quickly the selectors will change, we don't know. But he can view this now as a fantastic opportunity for him. To build a side of his own, to take forward, there's 12 Test matches before the next Ashes series in 2015."
England's batsmen have struggled in Australia, with 22-year-old newcomer Ben Stokes the only player to have scored a century for the tourists after reaching 120 in England's second innings in Perth.
England great Ian Botham laid the blame for England's failure squarely at the feet of their batsmen.
"The batters need to look at themselves," said the former all-rounder. "I'm sure the bowlers will be reminding the batsmen, 'We did our part, boys -- where were you?'
"To lose the Ashes is a massive thing when you've had it for three years. Those Australian boys will celebrate long into the night and I hope they have a great night because they've worked hard and they've totally outclassed England."
Former England batsman Geoff Boycott was typically outspoken in his criticism, declaring that Cook's men had "cocked it up big time".
He added: "Some of our coaching staff should have a serious look at themselves because we are on the down and Australia are on the up. We should be thinking and planning for 2015. Is our coach up to it?
"The top people have to decide -- (head coach) Andy Flower, are you going to be here next year? Are you staying or going? If you've had enough, go now.
"We have to be up for the challenge. We have to have the balls to do something."