Even on the back of a 62-14 victory over Northampton Saints on Saturday, the Pool 2 runners-up still faced the possibility of elimination with their fate in the hands of other teams.
But Premiership rivals Wasps did them a favour with a comfortable 26-7 victory over Ulster, securing Sarries' qualification as one of the three best second-placed teams, though they face a last-eight clash against a Leinster side who won all of their pool games.
Wasps were in command for virtually the entire contest and Guy Thompson, Tom Cruse, Willie le Roux and Jake Cooper-Wooley sealed a the bonus-point win, eliminating Ulster in the process.
Thanks to yesterday's 62-14 win over @SaintsRugby and today's results, Saracens will take their place in the Quarter-Finals of the @ChampionsCup to continue the defence of their title, get in there!!!
Fixture details to follow...
— Saracens Rugby Club (@Saracens) January 21, 2018
That victory kept Wasps' hopes of progression alive but they were soon extinguished by Munster, who sealed top spot in Pool 4 with an easy win over Castres.
Ian Keatley kicked 12 points and Keith Earls, Rhys Marshall, Simon Zebo, Alex Wootton and James Cronin all crossed as Munster cruised to a 48-3 success, leapfrogging Racing 92 into top spot.
Racing, who beat Leicester Tigers 23-20 with a late Maxime Machenaud penalty, still go through as one of the best runners-up - the Parisian side progressing alongside fellow second-placed sides Toulon and Sarries.
La Rochelle wrapped up top spot in Pool 1, finishing three points ahead of Wasps as they overcame Harlequins 16-7.
European Champions Cup quarter-final draw:
Leinster v Saracens
Scarlets v La Rochelle
Munster v Toulon
Clermont Auvergne v Racing 92
Photo Getty Images. Caption: Saracens will face Leinster in the last eight of the European Champions Cup