Career
He plays in Back Row usually as a Blindside Flanker. O'Callaghan has a Commerce degree from UCC.
O'Callaghan moved up through the Academy after joining in November 2009. He made his full debut against Ospreys in a RaboDirect Pro12 match on 8 October 2011.
O'Callaghan signed a Development contract with in March 2012. In January 2013, O'Callaghan agreed a two-year contract extension with In January 2015, O'Callaghan signed a one-year contract to remain with until at least June 2016. In December 2015, O'Callaghan signed a two-year contract extension with
O'Callaghan joined the Emerging squad for the 2013 IRB Tbilisi Cup in June 2013.
He came off the bench in the sides 19–8 defeat at the hands of South Africa President's XV on 11 June 2013.