Barrett made his debut for the All Blacks against Samoa early this year and started at fullback in the final test against the British and Irish Lions.
The 20-year-old suffered the injury in the Hurricanes Super Rugby semi-final loss to the Lions in Johannesburg and will require surgery, which means he won't be back in 2017.
"It's a pretty clear cut injury. The ligament has come off and it's basic reattachment," said assistant coach Ian Foster.
