 Kọ itẹsiwaju fun paragirafi yii - ONeill ti ṣakoso Grantham Town, Wycombe Wanderers, Norwich City, Leicester City, Celtic, Aston Villa ati Sunderland. Ó darí Leicester City dé ìdíje ife ẹyẹ Football League Cup lẹẹmẹta, ó sì gba ife ẹyẹ náà lẹẹmejì. Gẹgẹbi oludari Celtic laarin ọdun 2000 ati 2005, o mu ki ẹgbẹ naa gba awọn ami ẹyẹ meje pẹlu awọn akọle mẹta ti Scottish Premier League ati 2003 UEFA Cup Final : ó ṣe tán. Lẹyìn tí ó darapọ mọ Aston Villa, ó gba ipò kẹfà lẹẹmẹta lẹsẹkẹsẹ nínú ìdíje English Premier League, ó sì darí wọn sí ìdíje 2010 Football League Cup Final. 