The Chiefs said earlier this month the 22-year-old needed surgery on his right knee after suffering an injury on the All Blacks' end of year tour.
However, the prognosis was unclear when it came to whether he would be playing Super Rugby this year.
Coach Clayton McMillan though now does not expect Sititi to have "much on-field involvement".
Sititi enjoyed a stellar rookie campaign with the Chiefs last year with the club finishing Super Rugby Pacific runners-up to the Blues.
He went on to make his All Black debut playing 10 tests. He was named the All Blacks player of the year and also won World Rugby's men's Breakthrough Player of the Year award.
"Everyone saw the impact Wallace had last season and he's certainly a big loss for us, but our focus is now on supporting his recovery and eventual return to the field," McMillan said.
"I also know he will continue to contribute positively to our environment in any way he can."
The Chiefs open their season with a rematch of last year's final, against the Blues at Eden Park, on 15 February.
-RNZ