Mezue ahịrịokwu na-esonụ: A kpọrọ aha ya na ndị otu ọzụzụ nke Ireland maka asọmpi ahụ.
2013 Six Nations Championship na 17 Jenụwarị 2013, wee si na bench pụọ megide Wales na England. Mmerụ ahụ Mike McCarthy mere ka O'Callaghan bulie elu na mbido XV maka egwuregwu Ireland megide Scotland na 24 Febụwarị 2013. Nlọghachi McCarthy site na mmerụ ahụ wedara O'Callaghan n'ọkwa ọzọ na bench na 13 <unk> 13 draw na France. E wepụrụ O'Callaghan n'akụkụ mba ụwa, ebe Devin Toner nke Leinster na-ahọrọ maka ebe na bench megide Italy.