In his final season in charge, Cheika led Leinster to top of the table in the revamped 2009–10 Celtic League, with 13 victories from 18 starts. In the semifinal, Leinster beat Munster 16–6, before losing to the Ospreys 17–12 at home at the RDS. The team was also unable to retain their European title. Leinster beat Clermont Auvergne 29–28, however lost to eventual champions Toulouse 26–16.