Richie McCaw looks less than happy after his side's terrible start to the test in Dublin this morning.

Paul O'Connell fights for the ball during today's epic test against Ireland in Dublin.

Irish legend Brian O'Driscoll plays probably his final test against the All Blacks.

Ben Smith puts in the tackle during this morning's test against Ireland in Dublin.

Irish eyes are smiling as Ireland are awarded a try against the All Blacks.

Julian Savea gets the All Blacks on the board after a shocking start to the test match in Dublin.

Irish eyes certainly weren't smiling after the devastating last-second win for the All Blacks.

Coach Steve Hansen and skipper Richie McCaw share a moment after becoming the first team in professional rugby to celebrate a perfect season.

Aaron Cruden is mobbed after landing the sideline conversion to give the All Blacks an unlikely victory in Dublin.

The All Blacks celebrate as Aaron Cruden's conversion goes right down the middle.

Aaron Cruden's first attempt at the conversion missed, but he was allowed to retake it after the Irish team charged early.

Replacement Ryan Crotty goes over for the try that denied the Irish an historic victory in Dublin this morning.

The dressing room celebration is under way after the remarkable last-second victory for the All Blacks in Dublin.

All Blacks skipper Richie McCaw learnt a long time ago that you are never out of a game of rugby while you still have time on your side.

And he needed every ounce of that conviction today at the Aviva Stadium in Dublin to lead his men to a history-making victory over Ireland..

McCaw afterwards lauded the "belief" that allowed his team to conjure one of the great escapes in their history and claw their way to an improbable 24-22 victory and achieve test rugby's first perfect season of the professional era.

Getty Images BELIEF HOLDS: Richie McCaw learnt a long time ago that you are never out of a game of rugby while you still have time on your side.

When Ireland led 19-0 inside the first quarter and 22-7 at halftime, the All Blacks had looked in danger of seeing history turned on its head.

Instead of them celebrating their special sweep, it looked for all the world like it would be the Irish toasting their first victory over the All Blacks long into the Dublin evening.

The New Zealanders had been unable to haul in their fired-up opponents and when Irish fly-half Jonathan Sexton had a handy penalty that would have extended the Irish lead to eight with just five minutes or so remaining, the game looked like it had slipped away from the world champions.

But Sexton missed - "if that had gone over it was probably game over," McCaw conceded - and somehow the All Blacks survived a miscue or two over a dramatic finale to put replacement back Ryan Crotty in for the try.

That levelled the scores, handing five-eighth Aaron Cruden his biggest moment in test rugby with a sideline conversion at the second attempt.

"It comes down to belief," said McCaw after a sapping encounter in which he and his men had been outplayed for the great majority of it.

"When I was a young player and first started in the provincial game our captain at the time [Todd Blackadder] taught me something pretty important. We were down by a similar margin, 29 to very little. I thought the game was over and he said 'believe', and we got home in that game.

"Since then I've never, ever given up, and always been proud of All Black teams, that no matter whether you're behind, seemingly out of the game, you never stop believing there's a chance.

"We had 15 guys out there still believing today, right to the last minute, and it's amazing what can happen.

"For me as captain, as soon as I drop my head what are the other boys going to do? You've got to remember while there's still time, there's a chance."

McCaw's reference was to an unlikely Ranfurly Shield victory against Wellington in 2001 at the old Jade Stadium, and the lesson he learned that day has stayed with him.

The 32-year-old, in his 124th test, admitted the emotions were mixed in the changing sheds after such an unlikely victory today.

"It's a bit of a funny one I guess - there's relief and we're pretty happy to have got across the line, but we realise it could easily have gone the other way," McCaw said.

"Perhaps on another day it might have.

"Even though it was a pretty ugly performance from our point of view, we weren't allowed to play. To get across the line and believe and to get there, it's a pretty special bunch of men to be able to do that.

"It's a bit of a funny feeling but there's definitely a few smiles in there."

McCaw said Sexton's late penalty miss had provided just the sense of possibility that the All Blacks needed to pluck their rabbit from the hat.

"When that missed, you could see a sense of lift in the boys - there was still a chance," he reflected.

And perhaps in the Irish boys you could see they were trying to eat up as much time as they could. Sometimes when that happens an opportunity will come.

"We talked about it, that there will be a chance, and it's going to be about seeing if we're good enough to take it," McCaw said.

"That's the way it turned out."

Good enough and lucky enough. It was an effective combination on a special afternoon in Dublin when the All Blacks dug as deep as they've had to all season, and achieved the perfect season in such an imperfect manner.

You better believe it.