He was consulting specialists and might still require surgery.
"I would have loved to have gone back to Racing and to have given Europe another crack but I wasn't cleared to play, so it wasn't to be," Carter said.
"I wasn't cleared to play, so it's a blessing in disguise because I get to spend more time back here in NZ.
"I don't have a lot of rugby in me but I'm still loving it and enjoying it, so I guess this long break has helped me to phase into life after rugby."
He plans to return to the Steelers for another year, after being named the Japanese Top League's MVP and helping his team claim the title in his debut season.
"The beauty is that my second year in Japan doesn't start until after the World Cup.
"The Top League season there has been pushed back because of the World Cup, so I will have plenty of time to spend with my family. I thought I would get my body ready for my second season in Japan."
While this year's tournament promised to be tightly-contested, the two-time World Cup winner still backed the All Blacks to win a third-straight title.
"The beauty is that the rugby landscape has changed over the last few years. Now there is so much competition and we have seen the threats from the Irish, the Welsh, and the English and we all know South Africa and Australia will be good come World Cup time," he said.
"So it's not as one-sided as we all thought it was a couple of years ago, and that's exactly how we want it."