|Cardiff Blues (9) 23|
|Tries: Navidi, Fish Cons: G Davies, Anscombe Pens: Anscombe 3|
|Ospreys (7) 31|
|Tries: D Evans, Biggar, Grabham, John Cons: Biggar 4 Pens: Biggar|
Ospreys secured their place in the Pro12 play-offs with a convincing Judgement Day win over Cardiff Blues.
Despite Dan Evans' fine team try for Ospreys, Blues led 9-7 at half-time thanks to three Gareth Anscombe penalties.
Transformed after the break, however, Ospreys soared in front with stylish scores from Dan Biggar and Tom Grabham.
And although Josh Navidi and Dan Fish crossed for Blues, Ben John's try sealed Ospreys' bonus-point victory.
Thanks to Leinster's defeat by Ulster on Friday, Ospreys knew an eighth successive win against Blues would book their spot in the end-of-season play-offs.
They did so with a flourish, scoring four excellent tries and securing qualification for next term's European Champions Cup in the process.
With Wales head coach Warren Gatland watching, one of the most eagerly anticipated personal duels was between Blues fly-half Anscombe and Biggar, the current holder of the national 10 jersey.
Anscombe was the first to make an impression, slotting over two penalties as Blues dominated the early exchanges.
They benefited from an uncharacteristically sloppy start from Ospreys, whose handling errors denied them a try as a Josh Matavesi knock-on meant Dan Baker's effort was disallowed.
Blues were also left rueing their own mistakes when Tom Isaacs failed to gather from a promising position after Rhys Patchell's piercing run.
That proved to be costly as Ospreys produced a classy passage of play to score the opening try five minutes before the break.
After a neat exchange of passes between Biggar and Rhys Webb, loose-head prop Nicky Smith shoved Joaquin Tuculet out of the way before deftly offloading for Evans to touch down in the corner.
Their second try was similarly impressive, set up by a barnstorming break by captain Alun Wyn Jones, whose offload allowed Biggar to scamper over from 20 yards.
Momentum was well and truly with Ospreys at this point and they made it pay as swift hands from their backline set up Grabham to cross for their third score.
There was a nervy moment for the former Pro12 champions when Navidi swatted away a limp tackle from Scott Baldwin to score the Blues' first try.
Any hopes of a comeback were soon extinguished, however, as Ospreys moved into a commanding 31-16 lead with Biggar's penalty and an excellent team move culminating in John's try.
Blues replacement Fish intercepted and ran the length of the field to score with the last play of the game, but victory was already assured for Ospreys, who retain hope of claiming a fifth Pro12 title.
Cardiff Blues: Rhys Patchell; Lucas Amorosino, Tom Isaacs, Garyn Smith, Joaquin Tuculet, Gareth Anscombe, Lloyd Williams; Gethin Jenkins (capt), Kristian Dacey, Craig Mitchell, Chris Dicomidis, Filo Paulo, Josh Turnbull, Sam Warburton, Josh Navidi.
Replacements: Matthew Rees, Sam Hobbs, Scott Andrews, Jarrad Hoeata, Macauley Cook, Lewis Jones, Gareth Davies, Dan Fish.
Ospreys: Dan Evans; Tom Grabham, Ben John, Josh Matavesi, Eli Walker; Dan Biggar, Rhys Webb; Nicky Smith, Scott Baldwin, Aaron Jarvis, Lloyd Peers, Alun Wyn Jones (capt), Dan Lydiate, Justin Tipuric, Dan Baker.
Replacements: Sam Parry, Marc Thomas, Dmitri Arhip, Tyler Ardron, James King, Tom Habberfield, Sam Davies, Jonathan Spratt.
Referee: Nigel Owens (WRU)
Assistant referees: Rhys Thomas, Gwyn Morris (both WRU)
Citing Commissioner: Dennis Jones (WRU)
TMO: Gareth Simmonds (WRU)