Wales hooker Lloyd Burns will miss the Six Nations after being ruled out for three months with a neck injury.
The 27-year-old has enjoyed a startling rise to prominence, in 18 months going from Welsh Premiership club rugby to representing Wales at the World Cup.
But the Newport Gwent Dragons player now needs a lengthy period of rest.
"Lloyd has been advised to withdraw from rugby for at least three months in order to fully rehab his neck," said Dragons rugby director Robert Beale.
"We are obviously disappointed for Lloyd, particularly with the Six Nations coming up, but Lloyd's safety and welfare has to be paramount."
Burns, who has won seven caps, Huw Bennett and Ken Owens were Wales' World Cup squad hookers in New Zealand, with Ospreys forward Bennett emerging as first choice.
Injuries sidelined Matthew Rees and Richard Hibbard from the tournament, but they are now playing again.
WALES' SIX NATIONS FIXTURES
- 5 Feb:
v Ireland (a)
- 12 Feb:
v Scotland (h)
- 25 Feb:
v England (a)
- 10 March:
v Italy (h)
- 17 March:
v France (h)
Both players are likely to secure berths in Wales coach Warren Gatland's Six Nations squad when it is announced in around 10 days' time.
Burns' Dragons and Wales colleague, lock Luke Charteris, is also set to miss the competition because of injury, while Charteris' second-row colleague Alun-Wyn Jones is recovering from a toe problem that has threatened his participation.
Wales kick off their Six Nations campaign against Ireland in Dublin on 5 February.
The news comes as a further blow to the Dragons, who only last week were forced to announce the retirement of hooker Tom Willis, their former captain.