2009 Lions duo Luke Fitzgerald and Rob Kearney have both been ruled out after picking up injuries in the 38-18 defeat at the hands of New Zealand.
Fitzgerald, who made five appearances during last year's tour of South Africa, will be out of action for at least six weeks with a knee ligament injury while Kearney, who played in all three Tests, is due to undergo exploratory surgery also on a knee injury.
To make matters worst Ulster hooker Rory Best has been sidelined after fracturing a cheek bone, while three more Lions are doubts for the clash with the Pumas.
Lions legend Brian O'Driscoll picked up a shoulder injury while Tommy Bowe and Gordon D'Arcy both suffered calf strains.
All three players face a race to prove their fitness ahead of the clash with Declan Kidney preparing for the prospect of being without his entire first-choice three-quarter line.