Cobus Reinach scored a try as the Northampton Saints upset Clermont 34-21, while there were also European Champions Cup victories for Ulster, Exeter, Harlequins and the Scarlets.
While the outcome had no impact on the Pool 2 log standings, where Clermont are top and Northampton bottom, it was a morale-boosting result for the Saints, who registered their first Champions Cup win of the season.
Clermont controlled the first half and led 15-10 at the break courtesy of tries by Remi Grosso and Isaia Toeava plus a conversion and penalty from Morgan Parra. Teimana Harrison and Anthony Tuitavake went over for unconverted tries for the Saints.
Scrumhalf Nic Groom started for Northampton, but he was replaced by compatriot Reinach, who came on to score one of three unanswered tries in the second half to hand the hosts a superb victory.
Staying in this pool, defending champions Saracens had to settle for a 15-15 draw against the Ospreys and are in danger of missing out on a quarter-final spot. Saracens have to win their last pool match and hope the Ospreys don’t collect any log points in their final game.
In other notable results, Ulster clinched a thrilling 20-13 win against La Rochelle to go top in Pool 1, while a last-minute try saw Harlequins beat Wasps 33-28. With one round of fixtures remaining, there is still a realistic chance that Ulster, La Rochelle or Wasps top the log to secure automatic playoff qualification.
The Exeter Chiefs came away with all the log points on offer as they hammered Montpellier 41-10 to move up to second in Pool 3 and the Scarlets strengthened their chances of reaching the knockout stage with a 35-17 triumph over Bath.
Champions Cup results (Round 5):
Northampton Saints 34 Clermont 21
Ospreys 15 Saracens 15
Ulster 20 La Rochelle 13
Harlequins 33 Wasps 28
Exeter Chiefs 41 Montpellier 10
Bath 17 Scarlets 35
Remaining fixtures (Sunday):
Leinster vs Glasgow Warriors
Toulon vs Treviso
Racing vs Munster
Castres vs Leicester Tigers
Photo: Tony Marshall/Getty Images