Top 14 leaders Clermont were denied a late try by the TMO as they lost 16-13 to Grenoble in a high-paced encounter at the Stade des Alpes on Friday.
In a thrilling finish to the game, Clermont number eight Fritz Lee muscled his way over the line after a long build-up from the visitors but the TMO was unable to see clear grounding of the ball, turning down the try and handing Grenoble a memorable win.
Clermont led 10-9 at half time thanks to a try from wing Julien Malzieu but Grenoble wing Ratu Ratini put his team in front in dramatic fashion late on, sprinting 80m to score after Clermont skipper Aurelien Rougerie dropped the ball.
Clermont leave with a losing bonus point but will harbour many regrets having dominated for long periods and seeing two tries denied by the video ref after Benson Stanley had touched down late in the first half only for the score to be controversially cancelled due to obstruction.
Pens: Caminati 3
Yellow cards: Roodt, ThiÃ©ry
Pens: Parra 2
Yellow card: Lee
Grenoble: 15 Benjamin Thiery, 14 Ratu Ratini, 13 Geoffroy Messina, 12 Nigel Hunt, 11 Julien Caminati, 10 Blair Stewart, 9 Mathieu Loree, 8 Peter Kimlin, 7 Fabien Alexandre, 6 Jonathan Best, 5 Benjamin Hand, 4 Hendrik Roodt, 3 Dayna Edwards, 2 Anthony Hegarty, 1 Albertus Buckle.
Replacements: 16 Kenan Mutapcic, 17 Vincent Campo Castillo, 18 Andrew Farley, 19 Henry Vanderglas, 20 Rida Jaouher, 21 Fabien Gengenbacher, 22 James Hart, 23 Richard Choirat.
Clermont: 15 Jean Marcellin Buttin, 14 Julien Malzieu, 13 Aurelien Rougerie, 12 Benson Stanley, 11 Naipolioni Nalaga, 10 Brock James, 9 Morgan Parra, 8 Fritz Lee, 7 Alexandre Lapandry, 6 Gerhard Vosloo, 5 Nathan Hines, 4 Jamie Cudmore, 3 Davit Zirakashvili, 2 Ti'i Paulo, 1 Vincent Debaty,
Replacements: 16 Benjamin Kayser, 17 Thomas Domingo, 18 Julien Pierre, 19 Damien Chouly, 20 Ludovic Radosavljevic, 21 Noa Nakaitaci, 22 Lee Byrne, 23 Clement Ric.
Venue: Stade des Alpes
Referee: Laurent Cardona