British & Irish Lions hopeful Dafydd Jones suffered a setback in his bid to prove himself worthy of a place in Sir Clive Woodward's squad for this summer's tour of New Zealand when he was ruled out of Saturday's Six Nations Championship clash against Italy in Rome.
The Llanelli Scarlets flanker, who has a groin strain, failed a late fitness test on an injury that bothered him in the build-up to last weekend's victory over England in Cardiff.
Jones will be replaced in the starting line-up by Neath-Swansea Ospreys'
Jonathan Thomas, with Cardiff's Robin Sowden-Taylor taking over from Thomas on the bench.
"It is unfortunate to lose Dafydd at this late stage, but Jonathan Thomas is a more than able replacement for him," said Wales coach Mike Ruddock.
"Jonathan has been an integral member of our squad throughout the last year, and he has true international class."
Ruddock revealed Jones will undergo further medical checks on Monday to assess his fitness for the remaining championship games.