"It's unfortunate to lose Dafydd at this late stage but Jonathan Thomas is a more than able replacement for him in the back row," said Wales Coach Mike Ruddock. "Jonathan has been an integral member of our squad throughout the last year, Summer tour and the Lloyds TSB Autumn Series and he has true international class.
"Robin will offer us back row cover from the bench and his performances at regional level recently mean we have every confidence in him.
"Even though we have lost Dafydd there is still a huge amount of cover, quality and flexibility on the bench, as Ian Gough has played at blindside flanker as well as lock on many occasions for his region.
"Dafydd will undergo further examinations on Monday to assess his fitness for the remainder of the Championship.
"We have all arrived in Italy in good spirits and are now looking forward to getting down to the final part of our preparation to face a strong Azzuri side.
"We have closed the book on our victory over the Rugby World Champions at the Millennium Stadium last week and are firmly focussed on the task in hand."
The Ospreys back row forward Andy Lloyd has also travelled with squad to provide cover in that position.