England opener Alastair Cook knows his 100th Test will set the most exacting examination yet of his captaincy credentials.
Cook has not made it to a century of caps without the need for plenty of resilience and resourcefulness along the way.
He answered his critics as a batsman back in 2010, for example, with a century at The Oval and a mountain of runs to follow in England's historic victory here in Australia, when so few had apparently thought him worth his place at the top of the order alongside Andrew Strauss.
A few months later, having inherited the 50-over captaincy from Strauss, he confounded those who insisted he was simply not a viable one-day international batsman by operating at a strike rate and with a consistency which helped England win five consecutive series.
Only a year ago, Cook's Test captaincy tenure was cemented when England fought back from 1-0 down in India to win there for the first time since 1984/85.
Yet as he approaches the acid test of any remaining pretensions to a fourth successive Ashes series victory, at 2-0 down in Perth with three to play, 28-year-old Cook acknowledges the stakes are higher than ever this time.
"I think that's fair," he said.
"What happened in India was a big challenge after my third game as captain. (But) your next challenge is always the toughest and, after what's happened so far, I'd say so."
Cook must find the answers on two fronts, of course.
He needs to inspire his team and win the tactical battle as their leader. But he must also start making some runs - significantly more, at any rate, than the four he managed in two attempts before falling each time to Mitchell Johnson in England's landslide defeat in Adelaide.
Cook has had just three days to ready himself and his team to try to begin the revival, since Australia took England's last four wickets in 11 overs or so on the final morning of the second Test.
He said nonetheless: "I don't think it is a problem lifting the players.
"The hunger and desire that has been questioned has always been there in this side and we have another chance to show it this week.
"We have to make sure we're very clear individually of our plans both with bat and ball and, as a team, how we want to operate in this game."
It is highly unlikely, given Cook's drive to succeed and his unfussy demeanour, that the occasion of his 100th Test - one which, by a statistical quirk, he shares with his opposite number Michael Clarke - will be any sort of distraction.
Cook is rightly proud of his achievement but knows it is a sub-plot with the Ashes on the line.
He said: "It is a huge honour for me to be joining the 100 Club and one I never thought I'd get when I started off playing for Essex as a youngster and making the steps along the way.
"It is a special day and it will make it an even more special week if we can produce the performance we know we're capable of."
England's most obvious problem of the first two Tests has been an inability to cope with Johnson's express pace and bounce.
Cook has made a virtue since Adelaide of England's collective and individual honesty in defeat, and he was still citing some home truths on the eve of this third Test.
England, he agrees, have been found badly wanting against Johnson but must make sure they do not fret so much about the lethal left-armer that they become vulnerable to others in an attack Clarke rates the best in the world.
"I think our shot selection against him at certain times in this series has been quite poor and that's why he has had a lot of success," said Cook.
"It is very dangerous to start concentrating on one of their bowlers.
"They have a very good attack and have put us under pressure so far in this series."
However Cook's England fare over the next five days, he has established a body of work already - as his country's most prolific Test centurion - which indicates he will be around for several years to come yet.
He is not about to start predicting his own longevity, though.
"I have absolutely no idea. Who knows?" he said. "I have just got to cherish every one I play.
"I am very privileged to get 100 and I'd love to play a fair few more.
"It would be wrong just to assume anything in this game - it is a tough game. But if people still want me to play, I'll play for as long as I can."
Neither is Cook the type to revel in the praise accorded by his vice-captain Matt Prior, who is confident he will end up being England's "greatest" cricketer.
The captain said: "I don't think I'll ever put myself in that bracket.
"It was nice of Matty to say that but I think he was just being nice to me as captain.
"There are some great players to have played for England."