O'Callaghan is regarded as a surprise selection in some quarters given he is not a first choice with Ireland, yet that predicament is more down to bad luck than any weakness on his part.

The presence of Malcolm O'Kelly and Paul O'Connell in the Ireland squad means the Munster man has had his opportunities in the green shirt limited (he has won just 16 caps) yet his dynamism and all-round ability won him the nod ahead of Welshman Brent Cockbain.

O'Callaghan's rise to the Ireland senior squad has been something of an inevitability since he shone in the Ireland Under-19 side that won the World Youth Championship in 1998.

After spells in the Under-21s, Under-25s and A teams, he made his senior debut as a replacement against Wales in 2003 but has been banging his head against a brick wall for much of the two years since.

A tremendously physical player with good hands, the 26-year-old lock also gets around the pitch at a fair lick and is not afraid to stick his head in amongst the boots.