Harlequins prop Will Collier will miss the rest of the season with the knee injury sustained in Saturday's victory over Castres.
The 23-year-old tighthead, who recently signed a new contract until 2018, ruptured his anterior cruciate ligament in the Champions Cup match.
"Will has been ruled out for the remainder of this season," read a statement released by Harlequins.
Collier took to social media to thank well-wishers and vowed to return "fitter and stronger".
"Thanks for the kind messages," he tweeted. "Completely gutted to be missing the remainder of the season! Will be back...fitter and stronger."
Quins academy product Collier has played 69 times for the London side since making his debut in their 2011 LV= Cup match against Wasps in Abu Dhabi.
Collier made 20 appearances this season before suffering his season-ending injury.