Richie McCaw has identified the imposing physical presence of juggernaut Wales centre Jamie Roberts as a potential threat to his All Blacks team on Saturday.

Roberts, at 6ft 4in tall and almost 17 stone, has emerged during the past year among the most destructive centres in world rugby.

And New Zealand skipper McCaw saw enough of this summer's British and Irish Lions tour to realise just how influential 22-year-old Roberts can be in the rarefied Test match atmosphere.

"He had a great tour with the Lions," said McCaw. "He gave them a lot of go-forward against the Springboks.

"He's a big man, and someone we will keep an eye on. He was a major part of why the Lions played as well as they did in South Africa.

"I was really impressed by the Lions and was surprised how well they played. They could have won the series.

"They played a pretty good brand of rugby and put the Springboks under a lot of pressure. The Welsh players had quite an influence on that.

"Wales have good players, and we realise we are in for a tough match on Saturday. We would be idiots if we thought it was going to be easy."

New Zealand arrived in Cardiff following a poor Tri-Nations campaign by their standards, losing three games - all to South Africa - and finishing a distant eight points behind the Springboks in the final table.

But their record against Wales shows an unbeaten run since 1953, an overwhelming sequence of victories that includes five at the Millennium Stadium, approaching an average of 37 points a time.

Even without their fly-half superstar Dan Carter - his participation remains in doubt due to a calf muscle haematoma - the All Blacks are firm favourites for more away-day success.

McCaw though, who leads New Zealand for the 41st time on his 78th Test appearance, expects a high-octane occasion to replicate last year's clash when the All Blacks scored 20 unanswered points after trailing 9-6 early in the second-half.

"We had a tough middle part of the year, there is no doubt about that," he added.

"We had a few injuries, and maybe the senior players didn't lead like we could have done, but I don't think we are too far off.

"South Africa played some pretty good rugby in the Tri-Nations - they are playing probably the best rugby team in the world at the moment - but it would be easy to look at it all doom and gloom.

"Over the last few years, games against Wales have been better challenges, especially last year, when we didn't get away from them until the last few minutes.

"Wales come at you with a lot of passion and they pile into things. We are expecting the same this time."

McCaw, widely acknowledged as the world's leading openside flanker - and in many opinions, the planet's best player - will aim to do what he nearly always does and boss the critical breakdown area.

But Wales also possess a magnificent number seven in 88 times-capped Martyn Williams, and their intriguing head-to-head could go some way towards deciding the contest.

"I've got a lot of respect for Martyn," said McCaw. "He's played a lot of Test match rugby - he has been around a long time.

"The games I have played against him have been a good challenge.

"He plays with style and is a very good link-man. He is also good in defence, serving the team very well."

The All Blacks continued their preparations in Cardiff on Thursday, with head coach Graham Henry having announced a team showing six changes following last Saturday's win against Australia in Tokyo.

Stephen Donald will move off the bench to replace Carter if he is ruled out, while Henry's line-up also includes one new cap in 20-year-old Wellington Hurricanes wing Zac Guildford.

Guildford suffered personal tragedy earlier this year when his father died during the World Cup Under-20 tournament in Japan, a competition that New Zealand won.

Henry said: "Zac was in the New Zealand under-20 side that won the World Cup in Japan.

"It was a very sad situation for him because he lost his father during that tournament. His father was a spectator there, so that was very difficult for Zac.

"But he's handled it exceptionally well and used that situation as a motivating factor to try and repay his father for what he did for him.

"He has had his challenges during the year, and he's met them well. He is a mature young man."

Teams:

Wales: J Hook (Ospreys); L Halfpenny (Cardiff Blues), T Shanklin (Cardiff Blues), J Roberts (Cardiff Blues), S Williams (Ospreys); S Jones (Scarlets), G Cooper (Cardiff Blues); G Jenkins (Cardiff Blues), M Rees (Scarlets), P James (Ospreys), A-W Jones (Ospreys), L Charteris (Newport Gwent Dragons), A Powell (Cardiff Blues), M Williams (Cardiff Blues), R Jones (Ospreys, capt).

Replacements: H Bennett (Ospreys), Duncan Jones (Ospreys), B Davies (Cardiff Blues), Dafydd Jones (Scarlets), M Roberts (Scarlets), J Davies (Scarlets), T James (Cardiff Blues).

New Zealand: M Muliaina (Waikato Chiefs); C Jane, C Smith, M Nonu, Z Guildford (all Wellington Hurricanes); D Carter (Canterbury Crusaders), B Leonard (Waikato Chiefs); W Crockett (Canterbury Crusaders), A Hore, N Tialata (both Wellington Hurricanes), B Thorn (Canterbury Crusaders), J Eaton (Wellington Hurricanes), J Kaino (Auckland Blues), R McCaw (capt), K Read (both Canterbury Crusaders).

Replacements: C Flynn, O Franks (both Canterbury Crusaders), T Donnelly, A Thomson, J Cowan (all Otago Highlanders), S Donald (Waikato Chiefs), B Smith (Otago Highlanders).

Referee: Craig Joubert (South Africa).

Assistant referees: Mark Lawrence (South Africa) and Stuart Terheege (England).