Holders Saracens are facing a battle to avoid early elimination from the Champions Cup after their winter slump continued with a seventh consecutive defeat.
Full-back Scott Spedding’s long-range penalty two minutes from time saw Clermont Auvergne come from 13-0 down to beat Sarries 24-21 in France on Sunday.
The result leaves Saracens third in Pool 2 and needing to win their two remaining matches to have any hope of progressing.
“We were written off by lots of people,” said director of rugby Mark McCall.
“We attacked the game, competed for absolutely everything and fought for everything. We also played good rugby as well as defending much better, so it felt like we were much more like ourselves today.”
Saracens, who claimed a losing bonus points, scored tries in each half from scrum-half Ben Spencer and centre Alex Lozowski but the kicking of Morgan Parra, who landed six out of seven penalties, kept Clermont in touch.
England wing Elliot Daly, meanwhile, touched down twice as Wasps beat Pool 1 leaders La Rochelle 21-3 at the Ricoh Arena.
Replacement Tom Cruse added a third try for the hosts, who remain third in the group behind Ulster.
Wasps director of rugby Dai Young said: “If we can win our two games we have a chance of squeaking through.”