Harlequins prop Will Collier is to miss the rest of the season with a ruptured anterior cruciate ligament, the Premiership club have confirmed.
The 23-year-old sustained the injury during Saturday's European Champions Cup clash with Castres, which the Twickenham Stoop side went on to win 47-20.
Despite the victory, Quins missed out on progression on tries scored to Wasps, who took their place in the quarter-finals as one of three best-placed runners-up.
Collier has made 20 appearances in all competitions for Quins this term, and featured in all six of the club's Champions Cup pool fixtures.
He penned a new contract earlier this month, which will see him remain at the club until 2018.
Quins next face Bath in the Anglo-Welsh Cup on Saturday.