The club confirmed on Wednesday Ethan Blackadder will be absent after having surgery on an injured shoulder.
Blackadder - the son of former All Blacks and Crusaders captain Todd Blackadder - played a major role in Tasman’s unbeaten Mitre 10 Cup campaign.
He started in the Mako’s semi-final win over Auckland but then dislocated his left shoulder which required surgery.
He will now be aiming to return to action towards the end of the 2020 Super Rugby season.
The 24-year-old, who can play at blindside flanker and at the back of the scrum, has notched up seven appearances for the Crusaders over the past two seasons.
After the departure of experienced loose-forwards Matt Todd, Kieran Read and Jordan Taufua ahead of next season, Blackadder was being touted to play a major role in the Crusaders set-up next year.
