Saracens' place in the Champions Cup quarter-finals was secured after a tense 27-24 win over Racing 92, less than 24 hours after their Premiership relegation was announced.
The defending champions lost Billy Vunipola to injury and had Will Skelton sent off as they trailed at half-time.
Maro Itoje's second try levelled the scores and Owen Farrell's late penalty sealed an emotional victory.
Their spot in the last eight was sealed after Gloucester lost to Toulouse.
Gloucester had to beat the French side with a bonus point or by more than 12 points to take Saracens' place in the quarter-finals, but were beaten 35-14.
The day's results also mean Northampton go through to the last eight but Glasgow go out.
Saracens will travel to Leinster in the quarter-finals from 3-5 April, while Exeter host Northampton, Toulouse welcome Ulster and Clermont take on Racing 92.
Saracens seal late victory amid strange atmosphere
It was a subdued crowd before kick-off at Allianz Park as Saracens fans digested the news that their side would be playing in the Championship next season.
Sarries no longer have anything to play for in the Premiership, so needed victory against Racing 92 to keep not just their Champions Cup campaign but their entire season alive.
It seemed the players were using the relegation announcement as emotional fuel as they made a fast start, with Itoje barrelling across the line in the second minute after a kick to the corner.
Mako Vunipola added their second try from a similar line-out move shortly after, but it was not all smiles in north London.
Mako's brother Billy had left the field a few minutes earlier with a suspected broken forearm, his fourth such injury and bad news for England fans with Eddie Jones' Six Nations squad set to be announced on Monday.
The tables turned as Racing 92 got on the board when Elliot Daly missed a high ball from Finn Russell and Virimi Vakatawa grabbed hold of it to sprint across the tryline.
A Farrell penalty levelled things before Racing wing Louis Dupichot intercepted the fly-half's pass to score the French side's second try.
And things went from bad to worse as Vakatawa scored a second and Skelton was sent off for a late challenge on Brice Dulin.
'Lie down or stand up and rise'
Saracens faced the second half with 14 men and, according to coach Alex Sanderson speaking on BT Sport, had been told by Farrell at half-time they could "either lie down and roll over or stand up and rise".
But Racing were first off the mark after the break as Teddy Iribaren nailed a long-range penalty to take the lead up to seven, before Itoje crossed for his second a few minutes later to level things after Brad Barritt's cross-field kick to Duncan Taylor.
Whatever happens, Sarries will not be able to play in the Champions Cup next season because of their relegation and a draw would not have been enough to keep this term's campaign alive.
All the momentum was with Saracens then and Racing 92 joined them on 14 men as Bernard le Roux was given a yellow card for a late hit on Farrell.
Elliot Daly had the opportunity to take them ahead with a penalty from 45 metres out, but hooked it right and it was Farrell who stood up and claimed three points when Sarries were given a second chance shortly after.
The hosts erupted in celebration as Richard Wigglesworth kicked the ball into touch and the final whistle sounded to signal a crucial win.
'We had to do our talking on the pitch'
Saracens flanker Ben Earl said on BT sport: "That second 40 is everything this club is about. There have been a few obstacles this season but we knew we had to do our talking on the pitch today.
"The experienced heads in the changing room spoke a lot about our plan and it was about the rest of us putting it into practice.
"With what's gone on this week our focus shifts to Europe. We're going after that now and we know we're going to be a tough team to beat."
Line-ups
Saracens: Daly; Maitland, Taylor, Barritt (c), Segun; Farrell, Spencer; M Vunipola, George, Koch, Itoje, Kruis, Wray, Earl, B Vunipola.
Replacements: Lewington for Segun (47), Wigglesworth for Spencer (47), Barrington for M Vunipola (63), Lamositele for Koch (59), Skelton for B Vunipola (5).
Not Used: Singleton, Clark, Lozowski.
Sent Off: Skelton (39).
Racing 92: Dulin; Dupichot, Vakatawa, Chavancy (c), Imhoff; Russell, Iribaren; Ben Arous, Baubigny, Gomes Sa, Ryan, Palu, Lauret, Le Roux, Tanga.
Replacements: Trinh-Duc for Russell (75), Machenaud for Iribaren (56), Kolingar for Ben Arous (59), Le Guen for Baubigny (69), Oz for Gomes Sa (61), Chouzenoux for Lauret (59), Sanconnie for Tanga (75).
Not Used: Klemenczak.
Sin-bin: Iribaren (7), Le Roux (68).
Ref: Nigel Owens (Wales).