Cardiff Blues wing Lee Abdul is set to send the remainder of the season on the sidelines after undergoing surgery on Saturday on a double fracture of his ankle sustained in the game against the Gwent Dragons.
"This is obviously very sad news about Lee," said Blues coach Dai Young. "He has been a wonderful team member since being called up to the regional team.
"He has always given 100%, and we send him our best wishes for a speedy recovery."
There was better news on scrum-half Ryan Powell, who also injured an ankle against the Dragons.
He has only suffered bruising and will be fit for the Blues' next Celtic League game at the end of the month.
Nearly 40 players were involved in the first Wales Under 18 training session of the season. WRU National Performance Manager Gethin Watts is excited at the potential shown by the group and expects the Regional Under 18 Championship to hone their skills even further.