Ulster Schools' rugby captain John McCall has died during the IRB Under-19 World Cup tournament in South Africa.
John McCall was destined for higher honours in the game
The 18-year-old flanker collapsed during Ireland's opening game against New Zealand at the ABSA Stadium in Durban on Saturday afternoon.
McCall was rushed to St Augustine's Hospital but died soon after.
''It's a terrible tragedy,'' said IRFU President John Quilligan. ''Our sincere condolences go out to the McCall family.''
Initial reports that he sustained an injury after the collapse of a scrum have been discounted and it appears that he fell to the ground while he was running with the ball.
Mr Quilligan said that it would put a dampner on the Ireland's Triple Crown celebrations after hearing of the tragedy.
''It's terrible news and our heartfelt sympathy, goes out to everyone associated with the family.''
The senior Ireland team were not informed of the tragedy until after their 37-16 victory over Scotland in Dublin.
It is ironic that young McCall's uncle Brian was a member of the Ireland squad that last won the Triple Crown back in 1985.
The teenager led Royal Armagh to victory in the Ulster Schools' Cup over Campbell College on St Patrick's Day - the same day he received his Ireland Under-19 call-up.
His coach, former Ireland winger Kenny Hooks, said the players were devastated
at the tragedy.
"They all went to visit the family as a group this morning. They have found
it difficult because they are more than a team. They have spent so much time
together and there is a very close bond between them."
David Eakin the assistant coach at school said the news was hard to take in.
''It's shattering news,'' he said. ''John was an outstanding player and captain. He made a tremendous contribution to both his team and his school.''
The South Africa Rugby Football Union (SARFU) and International Rugby Board (IRB) have expressed shock and sadness in a joint statement.
It said: ''Flanker John McCall was taken to hospital after collapsing during the first half of the Irish match against New Zealand. At this stage the exact cause of death cannot be confirmed.
''SARFU and the IRB have pledged their full support and offer their deepest sympathies to the player's family as well as to the Irish under-19 team and management.''
The talented teenager led the Ulster Schools' side in this season's inter-provincial championship and was earmarked as a player with tremendous potential who would go far in the game.
He would have been 19 in August and was planning to study architecture at university.
His passing is the second tragedy to hit Ulster sport following the sudden death of GAA star Cormac McAnallen with a rare heart viral infection less than a month ago.