A 29–28 defeat by Biarritz on 10 April 2010 dashed the team's hopes of a first Heineken Cup semi-final appearance. A late Nicky Walker try in San Sebastien proved in vain. However, on 29 May 2010, the Ospreys won the 2009–10 Celtic League by defeating Leinster in the final by 17–12 at the RDS Arena in Dublin.