Saracens player ratings: Mark McCall's Sarries' 29-22 triumph at Mattioli Woods Welford Road was a testament to their lightning-fast start and an impressive second-half surge.
England lock Ollie Chessum will return to Leicester Tigers' starting XV on Sunday as his side host Saracens in the Gallagher Premiership.
England captain Maro Itoje will return to captain a Saracens side containing four of his international team-mates during the Guinness Six Nations when they host Harlequins in the Gallagher Premiership on Saturday.
Saracens player ratings: A dark day for former European heavyweights Saracens, who fell to an embarrassing 32-24 home defeat to an understrength Castres outfit.
There is no return for O’Mahony, whose last appearance came in the December 13 defeat at Castres.
This Saturday’s Investec Champions Cup trip to Munster is his club’s final fixture before Steve Borthwick’s January 14 announcement of his England Guinness Six Nations squad.
Bath will take a five-point lead at the top of the Gallagher Premiership into 2025 after blowing Saracens away at a raucous Recreation Ground.
Saints defeated the north Londoners three times last season and were led out by Nick Tompkins on his 200th appearance for the club, who were dealt a pre-match blow when Elliot Daly withdrew with a hamstring problem.
The Falcons lifted off the foot of the Gallagher Premiership table thanks to tries from Alex Hearle and Adam Radwan along with a Brett Connon penalty.
Newcastle moved off the bottom of the Gallagher Premiership table with a hard-fought 17-12 victory over Saracens at Kingston Park.