The Highlanders will be without Waisake Naholo and Fumiaki Tanaka when they face the Hurricanes at Forsyth Barr Stadium on Saturday.
Naholo, the leading try-scorer in last year's competition, fractured his leg during their 33-31 opening round defeat to the Blues on Friday, the same leg he fractured during his Test debut last July, and will be sidelined for six to eight weeks.
Japan international scrum-half Tanaka is the other casualty, having injured his calf during training for the Blues game, and is expected to be out for four weeks.
The defending champions' team doctor Greg Macleod, who will oversee Naholo's recovery, said the speedster's injury was less severe than the previous one.
"While this is very unfortunate for Waisake, the positive news is that this injury is not as bad as his last fracture," Macleod told the AAP.
"He is already managing well and it's expected his rehab will take six to eight weeks."
“Fumi has torn his calf and we expect the recovery to take 4 weeks."
Naholo was sidelined for nearly three months last year and then returned to his native Fiji where he received traditional healing.
The 24-year-old recovered in time to make the World Cup-winning squad and attributed his speedy recovery to a treatment of leaves and massages.
Highlanders head coach Jamie Joseph said that injuries are part of the game and that Naholo and Tanaka should now prioritise their recovery.
"To lose players for an extended period is always disappointing but you have to expect injuries to occur at some point," he said.
"As a group we simply deal with it and move on.
"The focus for the players now will be to rehab well and work to make themselves available again."