Argentina back rower Juan Fernandez Lobbe is out of the World Cup with a torn ligament in his left knee.
The Pumas vice-captain, who plays for Toulon, picked up the injury in the 13-12 win over Scotland on Sunday and is likely to be out for about six months.
Coach Santiago Phelan has yet to decide whether to call for a replacement.
If Argentina beat Georgia in their final game in Pool B and pick up a four-try bonus point, they will advance to the quarter-finals.
Pumas captain Felipe Contepomi said: "We haven't achieved anything yet. Now we are in the driving seat in playing Georgia and trying to get qualification. That's what we're here for."
Argentina had already lost Gonzalo Tiesi to a sprained ankle, but Rodrigo Roncero, who pulled a muscle in his left thigh, is expected to recover in time for Saturday's match.
Juan Manuel Leguizamon sprained his ankle and suffered a blow to an eye against Scotland but neither injury is thought to be serious.