Thomas had to be withdrawn at half time at the Stade de France, and had to watch from the sidelines as his team made a remarkable comeback which saw Wales clinch their third win on the trot in this year's tournament.
He has definitely been ruled out of the remainder of the 2005 Six Nations, and must be considered doubtful for his side's Heineken Cup quarter-final against Northampton Saints on April 1 (kick-off 20-30 local time).
That match takes place at the 37,000 capacity Municipal Stadium in Toulouse