London Irish scrum-half Tomas O'Leary has been ruled out for up to six months after having surgery on his back.
O'Leary, 29, has been unavailable for selection since his last appearance for the Exiles against Harlequins at Madejski Stadium on 28 October.
The Ireland international had a surgical procedure on his lower back on Tuesday, 4 December for a recent disc injury.
O'Leary signed for the Exiles in March after seven years with Munster.
The Cork-born half-back, who played 24 times for his country, has made just nine appearances for Irish this season.