Morgan Stoddart has undergone surgery on the broken left leg he suffered during Wales' opening World Cup warm-up Test against England at Twickenham on Saturday.
The Scarlets back is set to miss the World Cup, which kicks off in New Zealand on September 9.
The Welsh Rugby Union say Stoddart's operation was successful, although they have given no indication how long he will be sidelined for.
He remains in London's Charing Cross Hospital, and will return to Wales tomorrow.
"The good news about Morgan is that he has come through surgery successfully," said Prav Mathema, the WRU's national performance medical manager.
"He will now begin his rehabilitation programme back at the Scarlets.
"He travels back from London tomorrow, but it is impossible at this stage to put a time frame on his recovery."
Wales coach Warren Gatland, meanwhile, has received a triple fitness boost ahead of next Saturday's Millennium Stadium rematch against England.
Lee Byrne (knee), James Hook (shoulder) and Adam Jones (toe) have all been declared fully fit and back in contention for selection.
And Leigh Halfpenny (ankle) and Richard Hibbard (shoulder) both remain on course to be available for Wales' final pre-World Cup game against Argentina on August 20.
But Wales are stil waiting on the fitness of Scarlets pair Stephen Jones (calf) and Matthew Rees (neck), who were not involved against England two days ago.
Mathema added: "Stephen pulled out of the game at the weekend as a precaution with a tight calf, but we need to have a closer look at him in the early part of this week before we make a further judgement.
"Matthew is making normal progress after his injection, but it is also too soon to make a judgement on him."