The Ospreys recovered from their Heineken Cup mauling at the hands of Munster to record a morale-boosting, three tries to one, 28-19 Magners League victory over their west Wales rivals.
In front of their new director of coaching Scott Johnson the Ospreys came back from 19-11 down after an hour to score 17 unanswered points, including tries for Shane Williams and Lee Byrne, to keep their Magners title hopes intact.
The Ospreys were helped that they could unload a replacements bench including five internationals, which in the end was the difference between the sides.
The Scarlets' cause was not helped that they were forced into some late changes, most significantly, captain for the day Stephen Jones, who was a late withdrawal because of a hamstring injury.
As head coach Stuart Lancaster polishes the axe he will soon wield over his World Cup training squad, Exeter Chiefs coach Rob Baxter has backed Jack Nowell, Henry Slade and Luke Cowan-Dickie to be given a stay of execution.
Italy Under-20s held off a late Samoa blitz to retain their place in the World Rugby U20 Championship on Saturday and head coach Alessandro Troncon believes the experience will have served as a valuable lesson for his young troops.