Billy Vunipola receives treatment on his arm injury.
Injuries took a heavy toll on Saracens's resources, with the availability of Itoje alongside No 8, Billy Vunipola, having a notable impact.
Saracens, meanwhile, are facing the prospect of early elimination from European competition after their stalemate in Wales on Saturday.
Vunipola, playing only his second comeback game after a three-month absence with knee trouble, could now be a concern for the start of England's NatWest 6 Nations campaign, which begins against Italy in Rome on February 4.
" has an arm injury which we will obviously explore right away."
"(Michael Rhodes) has pulled a hamstring, so we had quite a lot to contend with. "It was just not good enough".
And Biggar kicked an equalising penalty eight minutes from time, setting up a gripping finale that saw Farrell land a 75th minute penalty before Biggar slotted an equalising strike four minutes later.
Saracens now realistically need a bonus-point victory over Allianz Park visitors Northampton next weekend to have any chance of progressing as a best runner-up. We are a tight group and that is what has seen us through some big games over the last couple of years and it is important that we got back to that.
"It is not in our hands". If they (Ospreys) beat Clermont next week, we are out of the competition if other results go (against us), and maybe we don't deserve to be in the competition because we have lost back-to-back games against Clermont and drew a game today.
"The Clermont home game happened (Saracens lost 46-14), and we had to deal with it".
Tandy said he was "unbelievably proud of the [Ospreys] players and the coaching staff for putting together a performance like that".
"When you play a fully-loaded Saracens team you know it's going to be an arm-wrestle, in greasy conditions, but we stuck to the task and our set-piece was more than about character - it was absolute quality".
"It's a special feat for the boys and we don't want it to finish in round six".
"We have to go to Clermont and be really positive because we know they'll have large parts of the game".
"But we truly believe we can go to France and play some positive rugby".