Carter confirmed he had signed for the Auckland-based team for the Super Rugby Aotearoa competition after his first training session with the side on Thursday.
The 10-week competition features all five of New Zealand’s Super Rugby sides and starts on 13 June.
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“It’s a chance to put the boots on … whether I play or not,” Carter told reporters in Auckland.
“I have not played for several months so it will be a number of weeks before I will be ready to be considered to play. And then only if my form warrants it. I’m fit but not rugby fit.”
The 38-year-old spent his entire professional career in New Zealand with the Canterbury Crusaders before he went to France after the 2015 Rugby World Cup.
He spent the last two seasons in Japan with Kobelco Steelers before the novel coronavirus outbreak ended the 2020 Top League campaign.
Carter said in April he would not be returning to Japan but that he had not retired, and a conversation with one of his sons convinced him he should sign with the Blues.
“I guess this gives me an opportunity to do what I love and to be able to go home at the end of the day and be with my family,” Carter said.
“Being (able to play) … in the same city where my kids go to school is a big factor behind me being here today.”
Blues coach Leon MacDonald, a former All Blacks and Crusaders teammate of Carter, said the side were lucky to have the three-times World Rugby Player of the Year in the squad.
“Some of the young guys are pinching themselves,” MacDonald said. “They don’t know whether to shake his hand or get an autograph.”