A red card for Cardiff Blues scrum-half Lloyd Williams proved the catalyst in Montpellier picking up a 35-24 Pool victory at the Arms Park on Sunday.
Up until the 25th minute sending-off, the game was in the balance after three Rhys Patchell penalties had Cardiff Blues 9-6 to the good.
But when Wales scrum-half Williams was given his marching orders by referee John Lacey after lifting opposite number Benoit Paillaugue above the shoulder and driving him to the ground, things swung massively in favour of the French side.
Montpellier failed to make the most of their numerical advantage though and credit to the Blues, who showed real character to stay right in touch for the remaining 55 minutes, only going beyond a nine-point deficit in the 78th minute.
Paillaugue kept the French side's score ticking over but he was matched by the highly-impressive Blues fly-half, 19-year-old Patchell, who not only scored all their points, including a drop-goal, but also produced a try saving tackle on BÃ©rard with an hour gone.
Paillaugue gave the visitors some breathing space with a penalty soon after for 22-18 and then the outstanding Georgian flanker Mamuka Gorgadze looked to have sealed the game when he stretched over the line to touch down.
However, Patchell slotted over two quick penalties - the second from distance - to reduce the lead to just three points with nine minutes remaining but Paillaugue made it 30-24.
With Cardiff having to throw caution to the wind and score a try of their own it was little surprise they conceded a third, a well worked one two minutes from time from Fijian master try scorer Timoci Nagusa, who touched down in the corner after being set up by Gorgadze.
For Cardiff Blues:
Pen: Patchell 7
Red card: L Williams (tip-tackle on 25 mins)
Tries: BÃ©rard, Gorgodze, Nagusa
Pen: Paillaugue 6
Cardiff Blues: 15 Jason Tovey, 14 Alex Cuthbert, 13 Gavin Evans, 12 Dafydd Hewitt, 11 Harry Robinson, 10 Rhys Patchell, 9 Lloyd Williams, 8 Andries Pretorius (c), 7 Sam Warburton, 6 Josh Navidi, 5 James Down, 4 Lou Reed, 3 Scott Andrews, 2 Marc Breeze, 1 Sam Hobbs.
Replacements: 16 Rhys Williams, 17 Tafa'ao Filise, 18 Benoit Bourrust, 19 Macauley Cook, 20 Robin Copeland, 21 Lewis Jones, 22 Ceri Sweeney, 23 Owen Williams.
Montpellier: 15 Benjamin Thiery, 14 Yoan Audrin, 13 Thomas Combezou, 12 Paul Bosch, 11 Pierre BÃ©rard, 10 Santiago Fernandez, 9 Benoit Paillaugue, 8 Johnnie Beattie, 7 Mamuka Gorgodze, 6 Alexandre Bias, 5 Aliki Fakate, 4 Drickus Hancke, 3 Maximiliano Bustos, 2 Agustin Creevy, 1 Mikheil Nariashvili.
Replacements: 16 Rassie van Vuuren, 17 Yvan Watremez, 18 Barry Fa'amausili, 19 Mickael Demarco, 20 Kelian Galletier, 21 Eric Escande, 22 Shontayne Hape, 23 Timoci Nagusa.
Referee: John Lacey (Ireland)
Assistant referees: Leo Colgan (Ireland), Michael Black (Ireland)
Television match official: Peter Ferguson (Ireland)
Timekeeper: Huw Lewis (Wales)