Ireland have confirmed that Paul O'Connell and Stephen Ferris will miss the critical showdown with Argentina.
O'Connell and Ferris are yet to recover from respective back and ankle injuries, ruling them out of the climax to the Guinness Series on Saturday week.
It is yet further bad news for Ireland, who were edged out 16-12 by South Africa on Saturday despite leading 12-3 at half-time.
Fiji are the next assignment - in a non-cap international at Thomond Park - but all eyes are trained on Ireland's meeting with Argentina, with defeat potentially dropping them into the third tier of seeds for the 2015 World Cup draw.
Ireland sank to eighth in the IRB's latest rankings, the gauge used to determine seedings for the 12 directly qualified teams for the tournament, which is being hosted by England.
Lock Donnacha Ryan and prop Cian Healy have passed mandatory concussion tests.