Frustrated Carter looks to snatch All Blacks spot
All Black Dan Carter smiles during the teams captains run at Eden Park in Auckland on September 13, 2013
The 31-year-old, who has played 97 times for his country, will be looking to put a disastrous run of injuries behind him on his latest comeback in Tokyo.
"The toughest thing is not being able to show what you can do," Carter said on Thursday. "It does motivate you to see other guys in the number 10 jersey. It's tough to accept."
Carter's latest setback came in September's 29-15 win over South Africa when he was clattered by Springboks hooker Bismarck du Plessis, damaging his shoulder.
"The shoulder's coming along well," Carter said. "I've started contact in the last couple of weeks and I'm getting my strength back."
All Blacks coach Steve Hansen will field an experimental side against Japan, making 14 changes from the team that beat Australia 41-33 in their last outing, although they will still be expected to win by a large margin.
But for Carter, widely regarded as the best fly-half to play the game, the Tokyo Test -- New Zealand's first against the Brave Blossoms on Japanese soil -- carries extra significance.
After a decade of dominating the number 10 shirt for New Zealand, the world's leading points scorer knows he faces a fight to become an automatic choice again with Aaron Cruden, Beauden Barrett and Tom Taylor all impressing in his absence.
"I'm proud how Aaron and Beauden have made the most of their chances," said Carter. "But all I can do is worry about what I'm doing."
Carter's form is set to come under the microscope with the All Blacks flying to Europe to complete a four-match tour against France, England and Ireland after playing Japan.
"There's been so much said about Dan that's been positive and then suddenly (people say) we can live without him," said Hansen. "That takes a bit of adjusting to, but Dan's just excited about getting back on the track after a horrific run of luck."
Captain Richie McCaw will start at loose forward, having also been troubled by injury this year, as New Zealand look ahead to their World Cup defence in 2015 by trying different combinations against Japan.
Saturday's match will be the first between the two teams outside of the World Cup after the All Blacks pulverised Japan 83-7 two years ago and 145-17 in 1995.
Carter will be hoping to come through the game unscathed after being described by Hansen as a "red-flag" player due to his injury problems.
"It's always frustrating to have to watch from the sideline," said Carter, set to take a six-month sabbatical next year to fix his various niggles and give himself the best chance to make his fourth World Cup.
"But the fact is the guys who've come in have been playing very well and that motivates me to keep improving."