Fijian wing Aisea Natoga scored a try in the dying seconds to help the Ospreys edge the Sale Sharks in their Anglo-Welsh Cup match on Friday night.
It was his third of the night, and stunned a side who felt they had done enough to secure their place in the semi-finals by notching the four-try bonus point, leading 36-20 after 54 minutes. But two yellow cards within four minutes with 10 minutes to go destroyed their structure and they lost 37-36.
Pool B remains the only undecided battleground, with Leicester losing 35-17 to Bath. It leaves Exeter needing only to win against lowly Worcester on Saturday to settle the issue, otherwise the Sharks will sneak though on the losing bonus point.
Going into Friday's games, just one point separated the top three in Pool B, while the semi-finalists in the other pools had been decided long before. Northampton, Saracens and Bath are now fighting for home advantage.
Cardiff Blues 35 Harlequins 5
Ospreys 37 Sale 36
Leicester 17 Bath 35
Newcastle 22 Newport Gwent Dragons 0
Worcester vs Exeter
Northampton vs Saracens
Gloucester vs Wasps
London Irish vs Scarlets
Photo: Michael Steele/Getty Images