Seven remains the perfect figure for Richie McCaw, says Graham Mourie.

Former All Blacks captain and openside flanker Mourie, who played 61 games (21 tests) between 1976-82, also reckons if McCaw is to surrender his No 7 jersey he should transfer to No 8.

Coach Steve Hansen's decision to start McCaw at No 8 against Ireland because Kieran Read has concussion has ignited discussions as to whether his 31-year-old skipper will swap positions in the future.

It is a topic that gains little traction with Mourie who says McCaw is still the king of the opensiders.

"Richie McCaw's strengths are his ability to get over the ball, to work with his backs and be a support player," Mourie said.

"No 7 and 8 are much more suited to him. Those positions are more homogenous than they were five years ago. He could play No6 but that is more the role of a strong defender. And the No6 has to be a strong ball carrier which is not a major strength of his game – he is not in the same class as a Jerome Kaino there."

McCaw says he has no desire to move from openside flanker, the position he has dominated since his international debut against Ireland in late 2001.

He is contracted to the New Zealand Rugby Union until 2015 and will be almost 35 if he lasts until the next World Cup.

Despite preparing to play his 106th test tomorrow night, Mourie doesn't believe McCaw's legs are losing their zip or his game has suffered because of his advancing years.

"I don't think he was ever that quick. But openside flankers are more stayers – not sprinters. They need to keep their pace consistent through a game. Some are very quick in the first 10 minutes but it's whether they are still going in the 80th that matters.

"Absolute pace is not the key to be a great No 7."

Preserving McCaw, Mourie added, is the key to wringing the best out of him. He questioned whether McCaw's workload was too heavy.

"Look at what they did to [former No 8] Rodney So'oialo. They ruined him by overplaying him. It's something people need to be aware of."

The pecking order of fetchers in the southern hemisphere has changed following Heinrich Brussow's recent omission from the Springboks, with McCaw duelling with the Wallabies' David Pocock for the title of the top No 7 Down Under.

Mourie says the New Zealander still deserves top billing, comparing the "old fox to the young fox".

"Pocock is a young man who is certainly playing well. He is very good at the breakdown and is a good ball carrier but he doesn't have the mana of McCaw.

"He has shown longevity. As a captain he has seen most things out there you can come up against and [he] can come up with the answers."

- © Fairfax NZ News