Sarcens are facing an injury scare over Richard Hill after he was helped off in his side's 20-3 Zurich Premiership loss to London Irish last weekend.
The first-choice England flanker departed holding his left knee in the 39th minute.
Saracens coach Rod Kafer said: 'I'm very worried about what his injury means to us in both the short and long-term.'
"Richard is a key player both to us and to England, but he is a tough lad and will be seen by the best medical staff."
A club spokesman added: "He is seeing a specialist later in the day once he has completed his work with the England squad."
Saracens face Bayonne in Round 1 of the European Challenge Cup. The first leg takes place at Stade Jean Dauger on Saturday, October 23, with the return leg taking place at Vicarage Road on Friday, October 29.
