Scarlets and Wales wing George North will be sidelined for three months after undergoing shoulder surgery.
The 18-year-old, who scored two tries on his Wales debut against South Africa in November, picked up the injury on international duty.
"Our policy with any soft tissue injury is to get a scan done immediately to ascertain the extent of the injury," said Scarlets head coach Nigel Davies.
"The scan revealed in this case that George required surgery to ensure there was no further damage.
"Potentially if not repaired, he could have suffered a dislocated shoulder which would have been a lot worse for such a young player at the very start of his career.
"In today's physically demanding game, it is crucial that the best interests of our players' long-term playing career are supported fully.
"It is obviously disappointing and frustrating for George and it's a blow to his colleagues at the Scarlets as he's had such a great start to his career in the senior team.
"But this is the right decision for him as a player and ultimately for the Scarlets in terms of getting him back fully fit and well and helping him develop further as a player with a very bright rugby career."
North appears unlikely to recover in time for start of the RBS Six Nations, which runs from February 4 to March 19.
It is a further blow for Scarlets, who are missing props Peter Edwards and Deacon Manu for up to 12 weeks with fractured forearms and Rhys Thomas is currently recovering from a fractured leg.
As a result, Scarlets have registered 20-year-old tighthead prop Simon Gardiner in their European squad.