New Zealand flyhalf Dan Carter may miss up to a month of the southern hemisphere Rugby Championship after aggravating an old calf injury in a blow for the All Blacks' title defence.
The 31-year-old Carter, twice IRB World Player of the Year, would have been a nailed-on starter for the tournament opener against Australia in Sydney on Saturday, but is expected to be sidelined for three to four weeks, coach Steve Hansen said at training on Tuesday.
Carter's absence opens the door for Aaron Cruden or Beauden Barrett to slot into the playmaker position, but would also force Hansen to re-consider his midfield options.
Hansen named just two midfield specialists in Ma'a Nonu and Conrad Smith in his 28-man squad, and had expected Carter to provide injury cover at inside centre.
"It will give us plenty of food for thought over the next 24 hours," Hansen told reporters in Porirua, near Wellington.
"It does make us think who will cover 12 (inside centre) so we will have a bit of thought on that before we name the team on Thursday."
Carter, who strained his left calf at training on Monday, will miss the return match against the Wallabies at Eden Park on Aug. 25 and would be scrambling to be fit for the All Blacks' third fixture against Argentina in Wellington on Sept. 8.
"It's disappointing for Dan ... It's not a biggie," Hansen said. "It's just something that is a nuisance more than anything else.
"It does sound dramatic because he's been there before and he's out for three or four weeks but talking to the 'Doc' it's that length (of time) because we want to make sure that he's dead right when he comes back."
Carter has had a number of leg injuries in recent years, and announced last week that he would take a six-month sabbatical from rugby after the All Blacks' northern hemisphere tour in November in the hope of prolonging his playing career up to the 2015 World Cup.
Carter's decision was influenced by his 32-year-old captain Richie McCaw, who recently returned to rugby refreshed after a similar sabbatical.
"It's a bit frustrating especially when the body was feeling good," said Carter, who had no idea how he had sustained the injury. "I've had injuries like this before so I know what I have to do to get back playing again.
"It's the first time I've done a calf this year so it's important that I just do the rehab so it doesn't happen again this year."
Hansen said Carter's planned break from rugby was unlikely to come at a better time.
"It really reiterates why he needs to have this extended break and get all the little niggles dead right so he can come back and play on a consistent basis," Hansen added.
"That's the nature of the beast, though. Rugby is a contact sport and DC will go away and work on what he has to do to come back."