Cardiff Blues have confirmed that centre Owen Williams has suffered a "significant injury to his cervical vertebrae and spinal cord."
The 22-year-old, who has played four times for Wales, was injured playing for Cardiff Blues at the World Cup 10s on Sunday.
The region said that he underwent an operation on Monday to stabilise a fracture and is currently recovering in hospital in Singapore.
His family and Blues staff are with him in hospital, and arrangements are now being made to arrange his safe transfer home "at an appropriate time."
The region and Williams' family have also thanked hundreds of people who have offered messages of support.
More top news
Council have until today to say if the plan to merge. Minister Leighton Andrews says joining together will create "significant savings"
Mainly cloudy, with a little patchy, light rain in the southeast this afternoon. Some brighter spells in the west at times.
A largely dry, cloudy and mild night with fog patches mainly confined to higher ground. Blustery along the coast.