Timoci Matanavou scored two tries for Toulouse as they ended Harlequins' unbeaten run and claimed an impressive 21-10 Heineken Cup victory at the Stoop on Friday.
Both sides came into the game level on points in Pool 6 but a powerful performance from the former Heineken Cup Champions sent a warning shot out to the rest of the teams in the tournament.
Toulouse controlled the pace and proceedings in a stunning first half of rugby which set the platform the visitors' victory.
Former New Zealand flyhalves Luke McAlister and Nick Evans exchanged penalties in the fifth and seventh minute respectively.
Toulouse struck with the first try after a neat chip forward from Luke Burgess. Quins failed to deal with the scrum-half's kick and number eight Louis Picamoles grabbed the loose ball to set-up field position.
Toulouse stretched Quins left and right before Picamoles and Thierry Dusatoir combined to send Matanavou over in the corner for the first of his tries.
It was roles reversed early in the second period as Quins came out of the changing rooms with the sort of performance that has seen them storm to victory in every game this season.
The hosts took the game to Toulouse and were rewarded for their early advantage with a Mike Brown try. Evans added the conversion to reduce the deficit to just a point.
But just as Quins look to be building another platform the power of Toulouse forced the four-times Champions back into the game with another Matanavou try to seal the victory.
Elsewhere Edinburgh lost their grip on top spot in Pool 2 after going down 25-8 against Cardiff Blues and will have to reverse the current trend against their Welsh rivals if they are to get back on course for only a second visit to the quarterfinals.
This defeat made it six in a row against the Blues and Michael Bradley's men can't afford a seventh in the return leg at Murrayfield next week. As for the Blues, they relied on the boot of Dan Parks to steer them to a third successive win and maintain the unbeaten record of the Welsh regions in this season's tournament.
If it wasn't pretty, it was still effective for the home side as they leapfrogged their main rivals for a spot in the last eight and put themselves on course for a return to the top flight.
Finally Ulster stretched their unbeaten run in the Heineken Cup at Ravenhill to nine games and kept themselves in the hunt in Pool 4 with this bonus point 25-10 victory over Italian outfit Aironi.
The Belfast-based side, who famously lift European rugby's prize back in 1999, kept themselves in the hunt for a quarterfinals spot in this tournament with this win over the Italian new boys.
Ulster now will watch with interest the other Pool clash between Clermont Auvergne, who they beat at Ravenhill, and Leicester, who they lost to in Welford Road, in France on Sunday.
Stephen Ferris, Adam D'arcy, Andrew Trimble, Paul Marshall and Paddy Jackson all crossed for tries for the home side but they found it tough going against their fellow Pro12 side.
All the Friday matches:
Harlequins 10 Toulouse 21
Tries: Matanavou 2
Pens: McAlister 3
Harlequins: 15 Mike Brown, 14 Seb Stegmann, 13 Matt Hopper, 12 Benjamin Urdapilleta, 11 Sam Smith, 10 Nick Evans, 9 Danny Care, 8 Nick Easter, 7 Chris Robshaw (c), 6 Maurie Fa'asavalu, 5 George Robson, 4 Tomas Vallejos, 3 James Johnston, 2 Chris Brooker, 1 Joe Marler
Replacements: 16 Joe Gray, 17 Mark Lambert, 18 Kyle Sinckler, 19 Charlie Matthews, 20 Luke Wallace, 21 Richard Bolt, 22 Rory Clegg, 23 Ugo Monye.
Toulouse: 15 Maxime Medard, 14 Vincent Clerc, 13 Florian Fritz, 12 Yannick Jauzion, 11 Timoci Matanavou, 10 Luke McAlister, 9 Luke Burgess, 8 Louis Picamoles, 7 Thierry Dusautoir, 6 Yannick Nyanga, 5 Yoann Maestri, 4 Grégory Lamboley, 3 Census Johnston, 2 Gary Botha, 1 Jean-Baptiste Poux.
Replacements: 16 William Servat, 17 Yohan Montes, 18 Johnson Falefa, 19 Romain Millo-Chluski, 20 Jean-Marc Doussain, 21 Yves Donguy, 22 Yann David , 23 Shaun Sowerby.
Cardiff Blues 25 Edinburgh 8
Pens: Parks 4
DGs: Parks 2
Cardiff Blues: 15 Leigh Halfpenny, 14 Alex Cuthbert, 13 Casey Laulala, 12 Jamie Roberts, 11 Chris Czekaj, 10 Dan Parks, 9 Lloyd Williams, 8 Xavier Rush, 7 Sam Warburton, 6 Michael Paterson, 5 Paul Tito, 4 Bradley Davies, 3 Tau Filise, 2 T Rhys Thomas, 1 Gethin Jenkins.
Replacements: 16 Ryan Tyrrell, 17 John Yapp, 18 Scott Andrews, 19 Maama Molitika, 20 Josh Navidi, 21 Richie Rees, 22 Ceri Sweeney, 23 Gavin Evans.
Edinburgh: 15 Chris Paterson, 14 Lee Jones, 13 Nick De Luca, 12 James King, 11 Tim Visser, 10 Harry Leonard, 9 Greig Laidlaw, 8 Stuart McInally, 7 Roddy Grant, 6 David Denton, 5 Esteban Lozada, 4 Sean Cox, 3 Geoff Cross, 2 Ross Ford, 1 Allan Jacobsen.
Replacements: 16 Steve Lawrie, 17 Kyle Traynor, 18 Jack Gilding, 19 Steve Turnbull, 20 Ross Rennie, 21 Mike Blair, 22 John Houston, 23 Tom Brown.
Ulster 31 Aironi 10
Tries: Ferris, D'Arcy, Trimble, Marshall, Jackson
Cons: Humphreys 3
Ulster: 15 Adam D'Arcy, 14 Andrew Trimble, 13 Darren Cave, 12 Nevin Spence, 11 Craig Gilroy, 10 Ian Humphreys, 9 Ruan Pienaar, 8 Pedrie Wannenburg, 7 Chris Henry, 6 Stephen Ferris, 5 Dan Tuohy, 4 Johann Muller (captain), 3 John Afoa, 2 Rory Best, 1 Paddy McAllister.
Replacements: 16 Andi Kyriacou, 17 Tom Court, 18 Adam Macklin, 19 Lewis Stevenson, 20 Robbie Diack, 21 Paul Marshall, 22 Paddy Jackson, 23 Stefan Terblanche.
Aironi: 15 Giiulio Toniolatti , 14 Sinoti Sinoti, 13 Roberto Quartaroli, 12 Gabriel Pizarro, 11 Matteo Pratichetti, 10 Tito Tebaldi, 9 Tyson Keats, 8 Josh Sole, 7 Simone Favaro, 6 Nicola Cattina, 5 Marco Bortolami, 4 Carlo del Fava, 3 Lorenzo Romano, 2 Fabio Ongaro, 1 Salvatore Perugini,
Replacements: 16 Tommaso D'Apice , 17 Alberto de Marchi, 18 Luca Redolfini, 19 George Biagi, 20 Filippo Ferrarini, 21 Giorgio Bronzini, 22 Naas Olivier, 23 Gilberto Pavan.
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