Argentina vice-captain Juan Martín Fernandez Lobbe will play no further part in the Rugby World Cup after sustaining a serious knee injury against Scotland on Sunday night.
The flanker limped off during the first half in Wellington. Scans reveal he has ruptured his left cruciate ligament.
The injury could keep the Toulon player out of rugby for six months.
Pumas coach Santiago Phelan is yet to decide whether to call for a replacement.
Argentina play Georgia in their final Pool B game in Palmerston North on Sunday.