Wales flanker Alisha Butchers will play no further part in the Rugby World Cup after sustaining a serious knee injury.
The 25-year-old fell awkwardly after making a superb line break during Wales' narrow victory over Scotland on Sunday.
Wales head coach Ioan Cunningham said a scan had revealed a "significant" injury.
"We are extremely disappointed for her, she is a huge part of our group, both on and off the field," he said.
"What is important now is that we get her fixed as quickly as possible and give her the best care so we can get her back on the field.
"It is a big loss, but it gives someone else an opportunity and the next person has got to step up."
Butchers will now return home for treatment, while Wales will make a decision regarding a replacement in the coming days.
Second row Georgia Evans sustained a shoulder injury in the game and is a doubt for Sunday's showdown against New Zealand.
"She has still got a sore shoulder, she can do a bit more training, but we will have to gauge the next 24 hours to see where she is at," Cunningham told BBC Sport Wales.
Wales are also monitoring the progress of another lock Gwen Crabb and prop Gwenllian Pyrs who missed Sunday's opener after picking up knocks in training.
"Gwen Crabb trained today and is coming back, Gwenllian Pyrs has done some more, they are up for selection," added Cunningham.
Analysis - Ceri Coleman-Phillips, BBC Sport Wales rugby reporter in Auckland
This is a huge blow for Wales as they prepare to take on the defending champions on their home soil.
Butchers is arguably Wales' best player, she had an outstanding Six Nations and was deservedly voted player of the year by the Welsh Rugby Writers Association in 2022.
She is key to Wales' lineout, a demon at the breakdown and has the footwork and pace to match most backs, as demonstrated against Scotland.
Butchers is no stranger to injury though, she missed the 2021 Six Nations after having an ankle operation, surgery which she was forced to fundraise for due to not having sufficient insurance.
But she now has professional contract on her side and along with her resilience and support network will surely bounce back yet again.
In the meantime, Wales can take solace from the strength in depth that has been built up in the squad.
Both tournament captain Siwan Lillicrap and Bethan Lewis are seasoned campaigners and able backrow deputies for Butchers.