A player who seems destined for the senior national side within a couple of seasons. O'Callaghan was a member of the winning under-19 World Cup side where he played in the second row alongside Damien Broughall. The six foot six inch second row/blindside flanker made the Ireland Under-21 squad at the beginning of this year when only 19. He was used as an impact substitute, a fact illustrated perfectly when he came on to score a try against Scotland.

Having turned 20 in March, O'Callaghan joined his brother Ultan in Cork Constitution's AIB League Division One success, again being sprung from the bench in several matches. Selected for the Ireland squad for the Under-21 SANZAR tournament in Argentina during the summer, he offered compelling evidence of his ability.

O'Callaghan was Ireland's player of the tournament, operating largely on the blindside flank.