Wellinton - New Zealand's World Cup campaign took a hit on Saturday when key men Richie McCaw and Dan Carter were both sidelined with late injuries before their final pool match against Canada.
McCaw suffered a flare-up in a long-standing foot problem but the extent of Carter's groin problem was less clear, as media speculated it could be serious enough to rule him out of the tournament.
The world's all-time leading points-scorer, 29, received the injury during kicking practice and would undergo a detailed assessment later, an All Blacks statement said. An update on his condition will be released on Sunday.
New Zealand's 3 News said team sources "absolutely" feared for Carter's participation in the rest of the tournament, but other media did not carry similar reports.
Carter had been named as captain after McCaw withdrew with "niggly" pain in his right foot, following surgery for a stress fracture in February. McCaw was also sidelined in May after recurring pain in same area.
The hosts have already qualified for the quarter-finals as they chase their first World Cup victory in 24 years.
"I'm not going to play and the reason is that my foot is a bit niggly," said McCaw, who earned a record 100th cap in New Zealand's win against France.
"It's a bit frustrating. I was pretty keen to play, it was important for me and the team. I got through training on Friday fine but I woke up a bit sore."
McCaw and Carter both missed New Zealand's game against Japan with a minor calf strain and a back problem respectively.
Against Canada, Colin Slade will now start in the number 10 jersey, with hooker Andrew Hore to captain the All Blacks for the first time. Andy Ellis comes onto the replacements bench.
McCaw's place at openside will be taken by Victor Vito, who will pack down alongside No 8 Kieran Read, returning from an ankle sprain.
Centre Sonny Bill Williams starts in place of Ma'a Nonu, Israel Dagg moves from fullback to right wing and Zac Guildford slots in at left wing instead of the injured Richard Kahui.
Jimmy Cowan comes in at scrum-half, with Piri Weepu moving to the bench as Henry continued to test his half-back pairings.
And Mils Muliaina will win his 99th cap at fullback, continuing his bid to become only the second All Black after McCaw to play 100 Tests.
Up front, Hore replaces Keven Mealamu at hooker, and Ali Williams comes in for Brad Thorn at lock.
The All Blacks opened their campaign here with a 41-10 win over Tonga before thrashing Japan 83-7 and most recently beating France 37-17, and will enter the knock-out phase of competition as pool winners.
Coach Graham Henry and his players have insisted that they are not undercooked, as was claimed in the 2007 World Cup when the Kiwis crashed out to the French in the quarters.
"We just want to make sure that the backbone of the team is ticking over all the time and the guys that need football get an opportunity because you just don't know what's going to happen on the injury front going forward and who is going to be required for finals football," Henry said earlier.
The match will be a milestone for Henry as a coach, he and assistants Steve Hansen and Wayne Smith celebrating their 100th All Blacks Test since taking over in the wake of New Zealand's failure in the 2003 World Cup.
The neutral might argue that Canada, who pulled off a surprise 25-20 win over Tonga before losing 46-19 to the French and drawing 23-23 with Japan, are on a hiding to nothing.
They have been hit by the absence through injury of goal-kicking fullback James Pritchard, but coach Kieran Crowley has otherwise named a full-strength Canadian team.