Scans have confirmed that Ennor ruptured the anterior cruciate ligament in his right knee during the North v South match in Wellington at the weekend.
Ennor, 23, who was named in the All Blacks squad on Sunday, will now see a specialist over the next few days, is expected to undergo surgery and be out of rugby for up to nine months.
All Blacks Head Coach Ian Foster said: "It's hugely disappointing for Braydon, but he is a strong young man and we'll be supporting him as he goes through his surgery and rehab over the next few months."
