They had needed to beat the Blues and for the Ospreys to lose in Aironi, but the Ospreys’ 12-10 victory in Italy put paid to the Scarlets’ ambitions.

The Scarlets fielded centre Regan King in his final match for the region before he joins French club Clermont Auvergne, while injuries meant the Blues were forced to play Jamie Roberts on the wing.

Honours had been shared at the end of a dramatic first half with the sides locked together at 20-20.

During a dramatic opening 40 minutes of changing fortunes both sides scored two tries.

In the first quarter the Scarlets took a 13-3 lead with by a try for prop Iestyn Thomas who finished off a drive from a lineout.

That was after Blues lock Michael Paterson had been sent to the sin-bin following a late challenge on outside-half Stephen Jones.

But the Blues came back with a converted try from wing Chris Czekaj, who was sent over by Roberts, and a Dan Parks penalty.

And 13-13 became 20-20 as both sides scored tries within two minutes of each other.

Ben Morgan scrambled over after slipping a tackle and Dafydd Hewitt benefited from some sloppy Scarlets defence when he escaped from a double tackle.

Parks failed with a drop-goal attempt at the end of the first half but he made amends with a successful drop-goal effort in the second minute after the restart as the Blues got their noses in front for the first time at 23-20.

The Blues suffered a setback when number eight Xavier Rush was taken from the field on a stretcher following a clash of heads with Scarlets prop Rhys Thomas.

And after Parks missed a penalty shot the Scarlets regained the lead when wing Sean Lamont went in down the left for an unconverted try. It was a double blow for the Blues as Martyn Williams was also sin-binned for a professional foul.

After Priestland grabbed a penalty to take the Blues out of losing bonus point territory, the Scarlets scored a bonus point try through Lamont.

But delight the victory was tempered by news that the Ospreys had qualified for the final play-off spot.