Saracens will be without number eight Ernst Joubert for the rest of the season following his injury in the Heineken Cup win over Ulster.
The South African forward underwent knee surgery on Thursday.
Other injury concerns for Saracens include Scotland centre Duncan Taylor and England full-back Alex Goode, with boss Mark McCall stating the club would be taking no risks with Goode's concussion.
"We've lost three important players and that's because of the nature of these games unfortunately," said McCall.
"Alex is OK, but we'll see how he goes. He was pretty shaken up afterwards.
"We're not going to take any gamble now with Alex, his health is far too important. It's highly unlikely he'll play this weekend.
"He could have got a serious neck injury given the way he fell."
Some good news for Saracens was the return of number eight Billy Vunipola from injury against Ulster, with McCall impressed by his performance.
"I thought Billy was wonderful given he only had four weeks off. He was magnificent."