The appointment of Liam Sheedy as Tipperary's new manager saw O'Brien take to a more prominent role. Tipperary remained undefeated during their 2008 league campaign and qualified for the decider against Galway. A Lar Corbett goal proved decisive in the 3-18 to 3-16 victory. It was O'Brien's first National League medal on the field of play. He later collected a second Munster medal as Tipperary continued their winning streak with a 2-21 to 0-19 defeat of a resurgent Clare. After scoring 1-4 in that game he was named man of the match.