Naholo, who is currently in a knee brace, has undergone an MRI scan – revealing a grade two MCL injury.
He suffered the injury at Highlanders training on Monday.
The injury could not come at a worse time for the Highlanders who are without All Blacks halfback Aaron Smith for a similar time frame due to an ankle injury.
It is also lousy timing for Naholo as he seeks a resurgence in form ahead of the Rugby World Cup, which starts in Japan in September.
