Carter pulled up with what appeared to be a leg or groin injury during Thursday's All Blacks training session at the University of Glamorgan, according to New Zealand media website www.stuff.co.nz.
The website says Carter appeared in immediate discomfort and changed training bibs with Aaron Cruden during a shortened work-out because of bad weather.
All Blacks coach Steve Hansen was questioned about Carter's fitness at a press conference in Cardiff on Thursday morning, which took place before training.
Asked if Carter was carrying an injury, Hansen emphatically replied: "No".
Cruden would be the obvious replacement if 93 times-capped Carter is sidelined, although there has been no official comment from the All Blacks camp since training.
The squad's final run-out is scheduled for the Millennium Stadium on Friday, when it is likely that any decision would be made.
Carter has scored 162 points in nine appearances against Wales, while the All Blacks, who are unbeaten in 19 Tests, conclude their autumn tour against England at Twickenham on Saturday week.
Injury cut short his World Cup campaign last year, but the All Blacks still lifted the Webb Ellis Trophy after they lost Carter during the competition's pool stages.
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