Carter's young understudy not afraid to step up to plate for the All Blacks – after all, he's already beaten cancer and tuberculosis
Dan Carter's groin had given way and his back-up Colin Slade followed suit. Suddenly Cruden, at just 22, shouldered the expectation of a nation.
It was a game of the highest pressure. Australia, who had beaten the All Blacks in the run up to the tournament, stood between the hosts and a place in the final.
It might have been too much for some. After all, New Zealand had found a way to fail at the previous five world cups, establishing themselves as the world power between tournaments, only to be trumped by the likes of France or South Africa.
Bringing the competition to New Zealand was meant to be the start of a long coronation, but as injuries mounted, the natives got jumpy.
Carter, the greatest player in the world, had been entrusted with delivering the Webb Ellis trophy, but now Cruden, making only his second start, was charged with banishing the Wallabies and Kiwi-born Quade Cooper.
Cruden delivered that win before succumbing to injury himself in the final, but perhaps there should have been less surprise at how well he reacted.
The setbacks in his career and personal life have been extraordinary. At just 5' 9" and 13st he faces an obvious physical challenge in Test rugby.
But before he reached the All Blacks, there were other serious hurdles to overcome.
Contracting tuberculosis meant he missed out on a chance to represent New Zealand schools. But the biggest test was to come when he was still a teenager.
At 19, he was diagnosed with testicular cancer that required surgery and a course of chemotherapy.
He kept the diagnosis to himself for a while and played in an important Ranfurly Shield game just days later. His recovery stalled his career, but after going into remission in late 2008, he has made up for lost time. He was made captain of the junior All Blacks side that captured world honours in 2009 and was later named player of the tournament.
The All Blacks took a longer-term view of his development and are reaping the rewards now. Like a few others in the squad, he was handed his debut against Ireland in 2010. However, he didn't make the following year's tour of Europe, but was instead left at home to work on his game management.
He has since filled one of the most thankless roles in sport as Carter's understudy. But as the latter's injuries have mounted, Cruden has delivered on the big occasions. He led his side brilliantly as the All Blacks recorded only their fourth win in Ellis Park earlier this year, while Irish fans will remember his superb performance in last year's third Test in Hamilton.
"Unfortunately for Dan, he's had a fair swagger on him for the last wee while and each game he gets, he'll be better and better," All Blacks captain Richie McCaw said.
"In some ways it's easier when you get to All Black level because there are 14 guys around you who are pretty good at what they do, you don't have to worry about anyone else."
With Carter ruled out through injury ahead of a six-month sabbatical, Cruden is expected to start against Ireland on Sunday and be their first choice No 10 well into 2014.
Some observers are of the belief he's on the verge of usurping Carter even before he picked up a knock in Twickenham.
"We're pretty lucky to have a guy like that who can slot in and since he made his debut in 2010, the growth we've seen in him has been phenomenal," McCaw continued.
"He's always had the talent, but dealing with things when under pressure and taking the right options, that comes with experience and he's made huge improvements in that area.
"He's directed the Chiefs' Super Rugby team to two championships and with that sort of form coming into Test rugby – I know it's a step-up from Super rugby – he slots in easily."
He's heading for 30 caps now. If Johnny Sexton doesn't make it, Ireland's out-half options Ian Madigan and Paddy Jackson have 11 caps between them, steepening the hill they have to climb this week.
"That's a fair big gap in terms of learning and experience and opportunity to make some errors and learn from them," Ireland coach Joe Schmidt agreed this week.
"It is important for us to get the right players around whoever goes into No 10 if it is not Johnny."
The All Blacks have made no secret of their immediate goal to finish the year unbeaten and Cruden is the man they again look to turn to in their bid to see out that little piece of history.
But they also have one eye on the World Cup in 2015 and having already overcome so much, getting Carter won't intimidate Cruden one bit.