UCD and Leinster academy prop Jeremy Loughman has seen his World Rugby U-20 Championship campaign come to an abrupt end after just over seven minutes' action.
Loughman suffered a badly broken nose in a collision with one of his own team-mates and will be sidelined for several weeks, with Cork Con's Liam O'Connor set to replace him.
He suffered the injury in the early stages of Tuesday's dramatic 18-16 win over Argentina when another player called from the standby list, Tomas Quinlan, was the hero with a last-gasp penalty.
O'Connor is uncapped at U-20 level and with scrum-half Charlie Rock having also made his bow against Argentina, the Munster Academy player will be the only uncapped player in the squad.
"I think when we were coming out we were hopeful to get through a tournament injury-free," said Ireland coach Nigel Carolan.
"But with the nature and the intensity of the games and physicality, there is always a chance you will lose somebody. Unfortunately, after seven or eight minutes Jeremy Loughman was on the receiving end of, I think, a headbutt from one of our own players.
"Unfortunately, it dislodged his nose, there was quite severe internal bleeding and he has had to withdraw from playing for the next number of weeks.
"But that unfortunate incident has created an opportunity for somebody else, and we are fortunate enough to call upon Liam O'Connor from Cork Con and Munster who played a part against France in our friendly game last week. Liam is on his way out to join the party with immediate effect."
Carolan said that the stifling heat had been hard to endure and they are expecting much the same when they play Scotland in Calvisanon on Saturday, which will also kick off at 4.30pm.
"It was very tough, particularly playing at the time of day we did and it's a major drain on all resources, physically and mentally," added the Irish coach.