2009 saw O'Sullivan enjoy his best season as manager of the Limerick senior footballers. After a disappointing league campaign championship, victories arrived over a fancied Tipperary side and Clare which meant Limerick qualified for a first Munster final since 2005. Cork stood in Limerick's way of a historic Munster championship win. Limerick stifled 'the Rebels' from the very start. For a time it looked as if Limerick would claim a first provincial title since 1896 but Cork, the red-hot favourites, scored key goals which saw them claim a narrow 2–6 to 0–11 victory. O'Sullivan's players took heart from this and entered the qualifiers at the final stage. A win in this game over Meath would have allowed Limerick enter the All-Ireland series for the first time in over a century. That game proved to be a difficult assignment. A narrow 1–13 to 2–9 victory for Meath saw Limerick exit the championship, however, it was a season to be proud for the Limerick footballers.