Bristol flanker Marco Mama has been ruled out for up to eight weeks after undergoing surgery on his thumb.
The 23-year-old suffered the injury in training and had successful surgery on the thumb ligament problem on Friday.
Bristol are hoping that Mama, who has made 18 appearances so far this season, will be available again in time for the end-of-season play-offs.
Prior to Friday's visit of Nottingham, Bristol lie second in the Championship, one point behind leaders Worcester.
Zimbabwean Mama joined the club's academy in 2009.