PREPARED TO WALK: All Blacks captain Richie McCaw has admitted he’ll retire from rugby before the next World Cup if his passion starts to wane.

Richie McCaw believes he can sustain his form and desire through to a fourth World Cup, but in a brutally frank admission, the All Blacks captain says he'll walk away from the team's shot at history if he feels either start to wane.

McCaw, in an exclusive interview with Sunday News to reflect on the All Blacks' history-making season, has offered a telling personal insight into the challenges he faces, at 32 and with a record 124 tests under his belt, making it through to England in 2015.

The veteran openside also delivered a chilling warning on the challenges looming for the world's No 1 side, believes Dan Carter's six-month extended leave will make or break his shot at personal World Cup redemption, and has urged a commonsense approach over the workload for star All Black Kieran Read over the next few years.

McCaw has had his challenges recently, with a painful foot injury requiring him to play the 2011 World Cup more or less on one leg, and some niggling ailments this year forcing him to miss more tests than he would have liked.

But the classy Cantab finished the year strongly, playing every minute of the last four tests as the All Blacks completed the first perfect season in the professional era. He admitted to a mix of relief and satisfaction about that, though he had never doubted his body's ability to see the task through.

But two more years? All Blacks coach Steve Hansen feels it's within his captain's grasp, but McCaw's thoughts are telling.

"People say ‘Are you hanging in till then?'. That's the wrong way to look at it," says McCaw who would love to lead the first All Black triumph on foreign turf. "You've got to really want to be there, to enjoy it, and be excited by it. It's not a matter of limping through just to be at a World Cup. You've got to enjoy it and perform all the way through.

"As long as I keep that desire, enjoyment and performance there, I'd love to be able to. [But] if for any reason that changes, you've got to do the right thing for the team and yourself."

It's left unsaid, but the "right thing" could be to walk away from the team he cherishes above all others.

"It's definitely do-able," he adds. "But if there is a reason to question things, we've got to have those honest conversations. Hopefully, you don't need to, but you trust that the team comes first. The big thing is not to get ahead of yourself. I'm looking at Super Rugby next year and doing that spot-on, because just hanging in there doesn't do anyone any good."

McCaw was naturally rapt with the 14-0 season, and loved the quality of the rugby produced and the character shown.

"We've adapted and added to the way we're trying to play," he says. "We're by no means perfect yet and we all understand that if we don't keep progressing we'll get overtaken. We saw over the last three weeks [of the tour] there's bugger all between all these teams and if you don't quite get it right you come unstuck. But we've got a good mix of guys introduced to test footy over the last couple of years, and some experience there. It's a good balance."

One thing concerns the skip: "We've had lopsided possession and territory counts over the last three tests, and we've got to work out why that is, because if you give teams enough time with the ball they're going to put you under pressure."

McCaw's thoughts on Carter are pertinent.

He knows too well how crucial that six-month break is for the 31-year-old, whose body badly needs to repair itself.

"Even if it was only for 20 minutes in that last game (against England) he showed how influential he still is, and if he can get his body right and get back playing regular rugby, there's no doubt he's still classy.

"[But] he's lucky to have that time now, because if he had to go through another year without the chance to get over these things, it would be a pretty hard road. Hopefully it's come at the right time."

In terms of Read, by consensus the best player on the planet, McCaw "100 per cent" agrees that the No 8's workload has to be handled sensibly.

"He's hugely important to the team now, and in the last couple of years his growth as a player and senior figure has been awesome to watch.

"It's not just him, either, there are other guys and it's all very well saying they're young, but if you keep thrashing them they'll come to a grinding halt.

"It's a fine line between looking at the here and now and looking at the big picture, but with Todd Blackadder and the All Black coaches we're lucky to have guys who can see past the next game-type thing."