The Scarlets lost the chance of a first Heineken Cup quarterfinal place in four years as they were beaten 29-17 by Northampton Saints in Pool at Parc y Scarlets.
The Welsh region went into the contest with genuine ambitions of a place in the knockout stages of European rugby's premier tournament for the first time since 2007 when they reached the semifinals.
But it was last season's beaten finalists who shone, grabbing a vital away win to keep their hopes of progressing in either the Heineken Cup or Amlin Challenge Cup alive.
Northampton's indiscipline cost them dearly in the opening exchanges when they lost wing Tom May to a yellow card after only two minutes for petulance and the Saints were down to 14-men.
Rhys Priestland and Steve Myler swapped penalties in a scrappy first half before the Tongan wing Viliame Iongi crossed for the home side's first try of the game after period of sustained pressure.
The Scarlets flyer latched onto a Priestland crosskick to give the Scarlets a 11 point lead before Myler landed a second penalty just before half-time to make it 14-6 to the Welsh side.
The Saints hit straight back after the break when prop Soane Tonga'uiha barged his way over from short-range to claw the Premiership outfit back to within a point of their hosts 14-13.
Myler and Priestland swapped penalties again, but Northampton's pressure on the home side gave them a 22-17 lead midway through the second half. The Scarlets threw the kitchen sink at the former champions in the dying moments of the game but couldn't breach Northampton's defence.
To add salt to the home side's wounds, they saw England full-back ran the length of the field for an interception try to seal an impressive rearguard action by last season's beaten finalists to clinch victory.
Pen: Priestland 4
Yellow card: Tom May (2 minutes - petulance)
Tries: Tonga'uiha, Foden
Cons: Myler, Lamb
Pen: Myler 5
Scarlets: 15 Liam Williams, 14 George North, 13 Scott Williams, 12 Jonathan Davies, 11 Viliame Iongi, 10 Rhys Priestland, 9 Gareth Davies, 8 Ben Morgan, 7 Rob McCusker, 6 Aaron Shingler, 5 Dominic Day, 4 Lou Reed, 3 Deacon Manu, 2 Matthew Rees, 1 Iestyn Thomas.
Replacements: 16 Ken Owens, 17 Phil John, 18 Rhodri Jones, 19 Josh Turnbull, 20 Jon Edwards, 21 Rhodri Williams, 22 Stephen Jones, 23 Gareth Maule.
Northampton: 15 Ben Foden, 14 Chris Ashton, 13 George Pisi, 12 Tom May, 11 Vas Artemyev, 10 Steve Myler, 9 Martin Roberts, 8 Roger Wilson, 7 Phil Dowson, 6 Calum Clark, 5 Mark Sorenson, 4 Samu Manoa, 3 Brian Mujati, 2 Dylan Hartley, 1 Soane Tonga'uiha.
Replacements: 16 Mikey Haywood, 17 Alex Waller, 18 Paul Doran-Jones, 19 Christian Day, 20 Ben Nutley, 21 Lee Dickson, 22 Ryan Lamb, 23 Scott Armstrong.
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