Former All Black Ma'a Nonu's French powerhouse Toulon booked their place in the European Champions Cup quarter-finals with a 19-14 win over English side Bath.
In other matches former Wallaby George Smith's Wasps sealed their last eight place with the English club recording a crushing 51-10 home victory over Irish side Leinster.
Ulster finished second behind Saracens in Pool One after picking up a bonus point in their 56-3 home demolition of Oyonnax, but their progress depends on tomorrow's results, when victory for Clermont Auvergne or Stade Francais could eliminate the Ulstermen.
London club Wasps ensured top spot in Pool Five - dubbed the group of death - by thrashing Leinster at the Ricoh Arena, picking up a bonus point after scoring seven tries to finish above four-times champions Toulon.
"It's a huge achievement by to get out of this group," Wasps director of rugby Dai Young told the club's website.
New England call-up Elliot Daly shone ahead of the Six Nations, the centre scoring a try and proving influential as the resurgent Wasps handed Leinster, who played a strong team despite having little at stake, their heaviest European defeat.
Leinster's miserable afternoon began when first-five Johnny Sexton was replaced in the ninth minute after suffering a head injury which threatens his Six Nations participation for Ireland.
While Toulon, who started Quade Cooper at five-eighth and O'Connor at fullback, are guaranteed an away quarter-final at Racing Metro, Wasps could enjoy the advantage of a home tie if Ospreys' result against Exeter Chiefs in Pool Two on Sunday goes their way.
In Pool One, already qualified Saracens made it six wins out of six, rounding off their pool campaign with a 28-17 victory at Toulouse.
English champions Saracens' 28-point tally after six matches guaranteed them a home quarter-final.
Former All Black Dan Carter's Racing topped Pool Three on 22 points despite the French team's unbeaten streak ending with a 22-5 defeat at Glasgow Warriors.
Victory for the Scottish side was not enough for them to advance to the quarter-finals as Northampton Saints won 22-10 at injury-ravaged Scarlets.
Northampton finished in second place on 19 points and will advance unless results go against them tomorrow.
Already qualified Leicester Tigers travel to Stade Francais with the French side needing at least a win to advance, while Munster visit Benetton Treviso.
Ospreys go to Exeter Chiefs in Pool Two and Clermont host Bordeaux Begles.