Kammala wannan jumla: O'Brien ya dawo daga rauni a gaban kakar 2015/16. Ya fito ne a Connacht a wasan da suka yi da Grenoble, kuma an sanya shi kyaftin din kungiyar Eagles. A watan Nuwambar 2015, an kira O'Brien a cikin tawagar Connacht don tafiya zuwa birnin Krasnoyarsk na Siberia don wasan gasar cin kofin kalubale na 2015-16. Ya fara wasan sa na farko a ranar 14 ga Nuwamba a wasan da suka yi da Enisey-STM, yana zuwa bayan minti 58 a matsayin wanda zai maye gurbin kyaftin John Muldoon. O'Brien ya yi wasansa na farko makonni biyu bayan haka a
2015<unk>16 Pro12 derby da Munster, yana fitowa daga benci don Eoghan Masterson yayin da Connacht ya ci nasara a Thomond Park a karon farko tun 1986. A watan Janairun 2016 an sanar da cewa O'Brien ya sanya hannu kan babban kwangila tare da kwangila, wanda ya gan shi ya zama memba na cikakken tawagar don kakar 2016-17.