The Ospreys have been left sweating on the fitness of Alun Wyn Jones after the second row suffered a serious shoulder injury.
Jones was replaced in the first half of Wales' shock defeat to Argentina following a heavy collision.
"Alun Wyn has damaged his AC joint," said Wales interim head coach Rob Howley.
"It doesn't look good for him at this moment in time. It is certainly going to test our strength in depth."
The Ospreys captain will undergo further tests and scans today which will determine the extent of the damage and whether he will miss any of the Heineken Cup.
The Swansea-based region are currently second in Pool Two, having beaten Benetton Treviso in Round One and fallen short against Leicester Tigers in Round Two.
They face Toulouse in their crucial December double-header and Jones' availability will be vital to their chances of securing qualification to the knockout stages.
They have already been boosted by the return to fitness of star duo Ryan Jones and Ashley Beck. The Welsh internationals were ruled out of last weekend's action with shoulder and hip injuries but have been cleared to return to full training.
Toulouse are not without their own injury concerns. Patricio Albacete was ruled out of the clash with Wales after suffering an eye injury against Racing Metro.
Albacete required surgery on his eye socket following the injury and is expected to be on the sidelines for up to 30 days, leaving him in a race to face the Ospreys.
