|Pro12, Judgement Day: Cardiff Blues v Ospreys|
|Cardiff Blues (21) 35|
|Tries: Dacey, N Williams, L Williams, Filise, Anscombe Cons: Anscombe 5|
|Ospreys (3) 17|
|Tries: Evans, James Cons: Davies 2 Pens: Davies|
Cardiff Blues claimed a first Pro12 win over Ospreys since 2010 with a dominant display at Judgement Day.
Blues blew their opponents away with tries from Kristian Dacey, Lloyd Williams and Nick Williams to lead 21-3 at half-time.
Taufa'ao Filise and Gareth Anscombe also crossed to seal a bonus point.
Dan Evans and Paul James replied, but Ospreys' fourth straight loss means they could drop out of the top four with Scarlets playing later.
Blues, meanwhile, leapfrog Connacht into seventh place, albeit with the Irish province hosting Leinster on Saturday night.
Without victory against the Ospreys since New Year's Eve 2010, the Blues sensed this might be their opportunity as their play-off chasing opponents had lost their last three games in succession.
Steve Tandy's side certainly looked out of sorts in a frenetic opening quarter, and their slow start was ruthlessly exploited by the rampant Blues.
Wales international hooker Dacey was the first to cross - running in unopposed from the back of a maul - before Lloyd Williams touched down with a sniping close-range finish.
The Blues played at a rapid pace, securing possession with good work at the breakdown and punching holes in the Ospreys' defence with strong, direct running.
One such carry came from Wales wing Alex Cuthbert, setting up Nick Williams to plough over, though Cuthbert's afternoon took a turn for the worst when he was sent to the sin bin for tackling Evans in the air.
The yellow card did not impact the match, as the Blues secured the bonus point four minutes into the second half as Filise stretched over.
The Blues were as impressive as the Ospreys were poor, and the fifth Blues try signified as much as Anscombe brilliantly gathered Willis Halaholo's kick, juggled and sped over.
Evans' try, having shrugged off a weak tackle from Anscombe, prompted a scattering of cheers from the travelling fans, and the more optimistic among them might have believed an improbable comeback was in the offing when replacement prop James bundled over.
But those scores were ultimately academic as the Ospreys slumped to a fourth successive defeat for the first time since 2014.
Ospreys head coach Steve Tandy:
"I did not think we showed enough fight or desire. At half-time you could one or two [of the players] were feeling sorry for themselves which was represented in the first ten minutes of the second-half which do you do not see to many times in Ospreys changing rooms if I am brutally honest."
"There were opportunities when the game was dead and buried to get the four tries [and a bonus point] which would have been little comfort.
"We have to do some soul searching in and around what and where we an put things right."
Cardiff Blues: Matthew Morgan; Alex Cuthbert, Rey Lee-Lo, Willis Halaholo, Rhun Williams; Gareth Anscombe, Lloyd Williams; Gethin Jenkins (capt), Kristian Dacey, Taufa'ao Filise, Jarrad Hoeata, Macauley Cook, Josh Navidi, Ellis Jenkins, Nick Williams.
Replacements: Matthew Rees, Rhys Gill, Anton Peikrishvili, James Down, Sion Bennett, Tomos Williams, Steve Shingler, Aled Summerhill.
Ospreys: Dan Evans: Keelan Giles, Ashley Beck, Josh Matavesi, Dafydd Howells; Sam Davies, Rhys Webb (Capt); Nicky Smith, Scott Baldwin, Brian Mujati, Bradley Davies, Rory Thornton, James King, Justin Tipuric, Dan Baker.
Replacements: Scott Otten, Paul James, Rhodri Jones, Lloyd Ashley, Tyler Ardron, Tom Habberfield, Luke Price, Kieron Fonotia
Referee: Andrew Brace (Ireland)
Assistant referees: Sean Gallagher (Ireland), Gywn Morris (Wales)
TMO: Neil Hennessy (Wales)