Wellington - Brodie Retallick has been ruled out of New Zealand's Test against Ireland in Chicago after suffering concussion.
The influential lock joins his second row team-mate Sam Whitelock on the injury list which leaves the All Blacks without their first-choice lock pairing.
A decision will be made once on the ground as to when Retallick and Whitelock (high ankle sprain) travel with the team, reports stuff.co.nz.
Coach Steve Hansen is set to welcome back first-choice scrumhalf Aaron Smith to the match-day squad after he served a ban for a toilet incident at a Christchurch airport.
Wellington loose forward/lock Vaea Fifita has been called in as a replacement for Retallick, joining uncapped Crusaders second-rower Scott Barrett.
However, Patrick Tuipulotu and Luke Romano are the frontrunners to start with either Barrett, Fifita or recalled Blues loose forward Steven Luatua providing cover from the bench.
"We've got three specialists locks and then Vaea can play both positions so reasonably comfortable," Hansen said.
"With Sam and Brodie not being there initially Scott Barrett and Fifita will be in the hunt."
Hansen confirmed Smith, who sat out the past two Tests in Durban and Auckland, would make a return next week.
Hurricanes scrumhalf TJ Perenara grabbed his opportunity in Smith's absence and it remains to be seen whether Smith starts or comes off the bench.
"I'd say so, yeah," Hansen said about whether Smith would be involved. He's the best halfback in the world."
Hansen said those All Blacks not required for the Irish Test who are eligible will instead turnout for New Zealand Maori, who take on a weakened USA team at the same venue one day prior.
"Hopefully we get the opportunity to give everyone a chance either starting or off the bench. It would be nice to give everyone a wee taste. You can't assess people if they're not given opportunities."