Michael Clarke faces a "sink-or-swim" challenge when he takes over from the injured Ricky Ponting as Australia captain in the Sydney Test.
Clarke could hardly have inherited the role at a trickier time, when his own batting form has deserted him and Australia are in grave danger of losing the Ashes outright on home soil for the first time in 24 years.
His opposite number Andrew Strauss noted that Clarke will have to learn quickly.
"It is a big day for Michael Clarke coming in and captaining in a Test match," said Strauss, who still recalls the shock to the system when he first took over in charge of England.
"As I found, though, you have to learn on the job - and you have to learn reasonably quickly. People sink or swim."
There will be no hiding place, with Australia needing to find inspiration from somewhere to avoid a first home Ashes defeat since 1986/87 and millions waiting to pass judgment on Clarke's efforts.
In fact, Clarke has managed to pass 50 only once in seven Ashes innings this winter - and Strauss acknowledges it can be harder for a captain to get things right when he is out of form with bat or ball.
"It's certainly a lot tougher," he said.
"If you've got the double whammy of the side not playing well and you're not playing well, there's almost not enough time in the day to think about your game and what you need to do in the team."