Clermont scrum-half and first choice kicker Morgan Parra is in doubt for his team's Heineken Cup quarter-final against Saracens at Vicarage Road.
The 23-year-old French international tore a left thigh muscle during Saturday's surprise 15-14 Top 14 defeat by struggling Biarritz.
Parra's status will become clearer later in the week when he undergoes further scans to determine how well the injury has healed, the club said in a statement.
His injury adds to Clermont's woes heading into the last-eight clash as they also have doubts over several other key players such as Alexandre Lapandry (back), France international wing Julien Malzieu (shoulder), Sitiveni Sivivatu (thigh) and Gerhard Vosloo (groin).
Clermont - who are aiming to reach the semi-finals for the first time and have made winning this their prime target this season - are already without Regan King (concussion), Anthony Floch (groin), Clement Ric (who has undergone an Achilles tendon operation) and Thomas Domingo (ruptured cruciate ligaments).