Havili had only just recently returned to playing after undergoing emergency bowel surgery at the start of March. He now has a fractured thumb, which he suffered towards the end of the clash with the Blues in Round five. It's unclear whether he will require surgery at this stage.
Injury woes have continued to hamper young Blackadder, who underwent knee surgery on Monday evening. He too had also just come back into the frame having recovered from a shoulder injury, which he picked up during the 2019 Mitre 10 Cup.
Blackadder and Havili join skipper Scott Barrett (foot) and Cullen Grace (thumb) on the sidelines.
The Crusaders sit five points clear of the Blues at the top of the Investec Super Rugby Aotearoa ladder and are fresh off a bye this week.
They host the Hurricanes, who are on a three-game winning streak, on Saturday at 7:05pm at Orangetheory Stadium. Get your tickets HERE.