Former New Zealand fly-half Andrew Mehrtens believes that the All Blacks will be less confident after the loss of their talisman Dan Carter but thinks that Piri Weepu can battle Colin Slade to wear the number 10 jersey.

"No-one saw this (Carter's injury) coming, I think for a while the All Blacks will be pretty nervous. But I don't think that it's removing any chance of New Zealand winning the World Cup," Mehrtens told ITV Sport's Martin Bayfield.

"The main problem is that Dan Carter has been so dominant in that fly-half position," added Mehrtens, "Because he's played week-in week-out for years it now becomes a question of how do you manage to bring a reserve through who has had hardly any game time?"

"I don’t think its as clear cut that Colin Slade comes straight in for Carter. Even though Slade is the understudy to Carter and it's best to have a natural number 10 come in, Weepu can fill in at fly-half too as he reads the game well and has brilliant kicking skills."

"Other guys have filled in this World Cup as well and have done very well so there is a lot to be positive about, but certainly we are less confident than before (Carter’s injury)."

"I guess Argentina are a good quarter-final opponent for the All Blacks as they are the least fancied of the teams in the last eight. This will give Slade or Weepu or whoever gets the nod at 10 to get some good game time."

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