London Irish captain and Ireland full back Conor O'Shea will be out for three months after breaking his ankle in Saturday's 26-6 defeat at Gloucester.
O'Shea suffered the injury in the final minute of the game and, following a successful operation to re-set his ankle, will be in plaster for six weeks. This is likely to rule him out of making an international comeback in the Six Nations Championship. O'Shea did not figure against South Africa last week.
Dick Best, Director of Rugby at London Irish, said: "We are all very upset and disappointed about Conor's injury.
"Fortunately, we have capable cover in Jarrod Cunningham and Rob Ashforth."