The All Blacks were Sunday sweating on the availability of captain Kieran Read for the looming British and Irish Lions series after the loose forward suffered a broken thumb.
Read left the field just before half-time during the Crusaders' 48-21 victory over the Cheetahs in Bloemfontein.
The bonus point win kept the unbeaten Crusaders at the top of the Super Rugby competition after nine rounds, but celebrations were muted by concern for Read.
"I think the whole of New Zealand is worried," Crusaders coach and All Black Scott Robertson told Fairfax Media after Read was rushed to hospital.
Crusaders assistant coach Jason Ryan told the New Zealand Herald it was "disappointing and will be concerning for the All Blacks."
Read, who has been capped 97 times and succeeded Richie McCaw as All Blacks captain following the victorious 2015 World Cup campaign, underwent surgery in a South African hospital.
The Crusaders issued a statement saying it usually takes six weeks to recover from such an operation. The first Test against the Lions is eight weeks away in Auckland on June 24.
Read, who missed the first six rounds of the Super competition following wrist surgery in the off-season, became the third senior All Black to go on the injured list in three days.
Jerome Kaino, who has played 77 Tests, will also be out of action for six weeks following a knee operation on Friday, while 60-Test fullback Ben Smith sprained an ankle during the Highlanders' win over the Stormers on Friday.
Israel Dagg, 61 caps, is believed to be at least two weeks away from returning to the Crusaders after injuring a knee in the third round of the competition.
Other injured All Blacks include Dane Coles, Nehe Milner-Skudder, Patrick Tuipulotu, Elliot Dixon, Lima Sopoaga and Tawera Kerr-Barlow.
For more rugby news, visit Rugby365.com