All Blacks locks Sam Whitelock and Tupou Vaa'i have been ruled out of New Zealand's second test against Ireland in Dunedin on Saturday.
Whitelock, who became the All Blacks' second-most capped player at the weekend, could also miss the third test in Wellington on July 16 after reporting a delayed onset concussion following the 42-19 win over the Irish at Eden Park.
World Rugby's new head injury protocols preclude players from being selected 12 days following a concussion.
"It's not ideal," All Blacks captain Sam Cane told reporters.
"Sam was awesome in the weekend. He became the second most capped All Black of all time which is hugely impressive.
"We'll no doubt miss his leadership and what he brings."
Coach Ian Foster will also be without Vaa'i after he tested positive for COVID-19.
Patrick Tuipulotu has been called up as a replacement following his recent return from a six-month stint in Japan.