England lock Maro Itoje has been ruled out for "a number of weeks" with a knee injury.
The Saracens star picked up a knock during his country's November internationals, featuring in all four Tests for Eddie Jones, and subsequent scans have revealed a chip in his patella.
It is not yet clear whether the issue will impact on Itoje's availability for the Six Nations, which gets under way on February 2 for England.
Saracens will have Mako Vunipola back for their European Champions Cup clash with Cardiff Blues on Sunday.
George Kruis (calf) is expected to be out for another week, while Billy Vunipola (arm), Liam Williams (hamstring) and David Strettle (foot) are among the other players unavailable for selection.