A second operation was required on the knee ligaments he damaged last November, adding at least three more months to his recovery time.
The world-class 31-year-old, who hasn't played since the serious injury suffered against France in Paris, had initially hoped to return late in the Hurricanes' Super Rugby campaign.
However, a lack of mobility meant a second round of surgery was required to remove scar tissue.
It leaves him with minimal chance of playing in the Rugby Championship, which opens when New Zealand face the Wallabies in Sydney on August 18.
Coles told Stuff he doesn't want to rush his recovery, to the point that he may not even be available for the All Blacks' late season tour to Japan and Europe.
"If it doesn't come right this year then I'll just have a good pre-season and head into next year," he said.