Buuxi weedha soo socota: Horan wuxuu sameeyay kulankiisii ugu horeeyay ee caalamiga ah ee ka dhanka ah Mareykanka inta lagu gudajiray xilli ciyaareedkii 1999-00, laakiin ma uusan ku guuleysan kulan kale ilaa xilli ciyaareedkii 2002-03, kaasoo ka soo horjeeday Fiji. Wuxuu booskiisa ku waayay Reggie Corrigan intii lagu jiray Koobka Adduunka ee Rugby 2003 iyo 2004 iyo 2005 Six Nations Championship, laakiin bandhigyo joogto ah oo xoog leh oo loogu talagalay Munster ayaa u arkay inuu dib u helay booskiisa kooxda. Wuxuu qabtay booskiisa
2006, 2007, 2008 iyo 2009 Six Nations Championship, oo bilaabay ciyaar kasta oo ka mid ah ololihii Grand Slam ee guusha ee Ireland. Waxa uu sidoo kale qayb muhiim ah ka ahaa kooxda Eddie O'Sullivan ee 2007 Rugby World Cup. Wuxuu seegi jiray Imtixaanka Nofeembar 2009 ka dib markii qalliin wadne lagu sameeyay, wuxuuna booskiisa ku waayay Cian Healy, oo haystay booska madaxa-furitaanka inta lagu gudajiray Horyaalka Lixda Qaran ee 2010. Horan wuxuu la ciyaaray Barbarians F.C. iyo New Zealand Maori intii lagu jiray Imtixaanka Xagaaga ee Ireland ee 2010, laakiin waxaa laga saaray Imtixaanka Nofeembar 2010 isagoo gacanta ka jabay. Wuxuu ka maqnaa 2011 Six Nations Championship, laakiin waxaa loo xushay kooxda tababarka ee Ireland ee loogu talagalay 2011 Koobka Adduunka ee Rugby World Cup ee bishii Agoosto 2011. Wuxuu la ciyaaray Scotland, laakiin wuu ka maqnaa xulashada kooxda ugu dambeysa ee Koobka Adduunka.