Leicester Tigers lock Tomás Lavanini will have surgery on a syndesmosis injury sustained during the European Challenge Cup semi-final against Toulon.
The second rower suffered the high ankle injury in the final minutes of the fixture before leaving the field with the help of medical staff.
It is expected that he will be unavailable to play until late December.
Director of Rugby Geordan Murphy admitted the loss of Lavanini was disappointing for the club.
“Tomás is a world-class forward, who plays a big role in our squad,” said Murphy.
“We’re disappointed to not have him available for the final fixture of the current campaign and opening months of next season.
“We are fortunate to have senior players in our second-row stocks in Calum Green, Harry Wells, Blake Enever, as well as a crop of exciting youngsters making their way up the ranks.
“He is a model professional and I have no doubt that, with the help of our medical team, he will get through his rehabilitation and hit the ground running when fully recovered.”