ALL Blacks flyhalf Dan Carter could be in doubt for their rugby World Cup Pool A clash against Japan on Friday after he suffered a sore back in the tournament opener against Tonga.!

Carter was hit hard in the 41-10 victory over the Pacific islanders last Friday and had been receiving ice treatment but was slowly recovering, assistant coach Steve Hansen said on Tuesday.!

"Dan's coming right. He got hit in the back, so he's a bit sore. We'll just have to see how he goes," Hansen said, while adding that veterans Mils Muliaina and Conrad Smith could be in line for a start against the Japanese as the selectors continue to tinker with their starting side.!

"You might see Conrad Smith come back into the centres. I don't think too many people are going to see that as a negative.!

"You might see someone like Mils (Muliaina) get a start so we can sort out which of those two is playing the best to go through the rest of the tournament," he added in reference to Muliaina's battle with Israel Dagg for the fullback jersey.!

Since the Tongan game there have been increasing appeals from former All Blacks and fans alike for the coaching panel to pick their strongest side for the remaining pool games.!

Team selection has been a bone of contention for the rugby-mad New Zealand public ever since the last World Cup, when the same coaching panel experimented with a policy of rotation at the cost of building combinations within the team.!

Many pundits believe the All Blacks earliest exit from a World Cup tournament, courtesy of a stunning 20-18 defeat at the hands of France in the 2007 quarter-final, was directly attributable to the policy.!

Reuters