A fourth-minute red card for full-back Jared Payne helped Saracens book their spot in the Heineken Cup semis as they beat Ulster 17-15 on Saturday.
The result means Saracens will face Clermont in the last-four at Twickenham, with Ulster, who were top seeds, having pushed them all the way.
A double from Chris Ashton and a try from Mouritz Botha saw an intensely physical Saracens storm the Ravenhil fortress.
The hosts responded with kicks from Ruan Pienaar and Irish international Paddy Jackson, but could not quite close the deal.
It was a spirited and courageous effort from the fourteen men, but ultimately Sarries' greater numbers proved decisive. How different this result might have been was it not for a piece of careless indiscipline.
The game got off to a frenetic start, with both teams charging into each other with a shuddering intensity. Farrell had a golden chance to establish a lead for his side on two minutes, but missed the effort.
The physicality of the opening minutes was only halted when Alex Goode sustained what looked like a nasty injury, following a collision with Payne that saw the English full-back taken out in the air. The Ulster full-back was red-carded for his recklessness, giving Sarries a decided advantage.
It was an ugly challenge, and one that seemed to have dire implications for Ulster's chances.
Ulster battled on valiantly thereafter, but were clearly hamstrung by their numerical disadvantage. That said the Irish side's resistance was remarkable in the circumstances.
Incredibly, the game was still scoreless after fifteen minutes. It was at that point that talisman Pienaar gave his side an unlikely lead to make it 3-0.
And the South African scrum-half had a gilt-edged chance to increase the lead a couple of minutes later, but was off-kilter with the kick.
But the extra man was always going to count at some stage, and following a powerful Sarries scrum, Ashton sliced through a gaping hole in the Ulster defence to dive over for a well-taken try. Farrell again was off target with the kick to leave it 5-3.
The momentum was irrefutably with the Premiership side at this stage, albeit with the hosts hanging in really well. Following a sublimely executed rolling maul on 28 minutes, Saracens inevitably conceded a penalty with the home pack just yards from the line. This time, Pienaar made no mistake with the three points to restore Ulster's lead to 5-6.
Ulster's playmaker had another opportunity 37 minutes with a long range effort from way over the halfway line, but it fell just short. But he made amends on the cusp of half time when he slotted another penalty to make it 5-9 to the Ravenhill men.
It was a truly absorbing half of rugby, packed with incident and bone crunching ferocity. Saracens seemed a little off colour during the first period it has to be said, but given their travails, Ulster would have been delighted with their slender lead.
At the start of the second-half, it was very much game on. But Saracens' additional numbers again proved telling on 48 minutes when Botha finished off some slick handling, following a period of concerted Sarries' pressure. Farrell, who was having an evening to forget, again couldn't add the extra points, making it 10-9 to the Englishmen.
Jackson had a good chance to restore Ulster's advantage on 51 minutes, but his kick hit the uprights.
Farrell's jitters continued, however, to leave it a one point ball game. But the visitors were beginning to turn the screw determinedly at this stage, and with Ulster severely depleted, they assuredly scented blood. Thus, with the visitors camped in the home 22, Ulster eventually conceded a penalty on 67 minutes.
From the ensuing advantage, Farrell launched a beautiful cross-field kick that a grateful and unmarked Ashton touched down. Farrell made no mistake with the conversion on this occasion to make it 17-9 to the Premiership outfit.
Given the undoubted dominance of his side, the try had an air of inevitability about it. But the hosts remained stubbornly defiant, and Jackson reduced the deficit on 70 minutes with a sweetly-struck kick.
The Irish fly-half narrowed the gap even further two minutes later to an incredible two points to make it 17-15.
Ulster courageously battered the Sarries' rearguard in the last few minutes. It was brave and committed stuff, but this was destined to be Saracens' day. How different it might have been if Ulster had retained fifteen players on the pitch. For a delighted Saracens, it's onwards and upwards.
Pen: Pienaar 3, Jackson 2
Tries: Ashton 2, Botha
Ulster: 15 Jared Payne, 14 Andrew Trimble, 13 Darren Cave, 12 Luke Marshall, 11 Tommy Bowe, 10 Paddy Jackson, 9 Ruan Pienaar, 8 Nick Williams, 7 Chris Henry, 6 Roger Wilson, 5 Dan Tuohy, 4 Johann Muller (c), 3 John Afoa, 2 Rory Best, 1 Tom Court.
Replacements: 16 Rob Herring, 17 Andrew Warwick, 18 Ricky Lutton, 19 Iain Henderson, 20 Stephen Ferris, 21 Robbie Diack, 22 Paul Marshall, 23 Craig Gilroy.
Saracens: 15 Alex Goode, 14 Chris Ashton, 13 Duncan Taylor, 12 Brad Barritt, 11 David Strettle, 10 Owen Farrell, 9 Richard Wigglesworth, 8 Ernst Joubert, 7 Jacques Burger, 6 Billy Vunipola, 5 Mouritz Botha, 4 Steve Borthwick (c), 3 James Johnston, 2 Schalk Brits, 1 Mako Vunipola.
Replacements: 16 Jamie George, 17 Richard Barrington, 18 Matt Stevens, 19 Eoin Sheriff, 20 Kelly Brown, 21 Neil de Kock, 22 Charlie Hodgson, 23 Chris Wyles.
Referee: JÃ©rÃ´me GarcÃ¨s (France)
Assistant referees: Mathieu Raynal (France), CÃ©dric Marchat (France)
TMO: Eric Gauzins (France)
By Rory McGimpsey