Defending champions Leinster went top of the Magners League with a three-tries-to-two victory over the Scarlets at Parc y Scarlets.
The Irish Province were always in control of a contest they led 20-0 after only 26 minutes with tries for wing Isikeli Nacewa and flanker Cameron Jowitt.
The Scarlets, who were without their Wales quartet Stephen Jones, Mark Jones, Matthew Rees and Dafydd Jones, and then lost playmaker Regan King with a first-half hamstring injury, came back either side of half-time with tries for scrum-half Martin Roberts and prop Deacon Manu.
But Leinster had the final say with a try for captain Shane Jennings and a penalty goal for Felipe Contepomi, who provided 16 points with the boot.
The Scarlets made a flawed start to the match with Contepomi converting a penalty to give the visitors a 3-0 lead on three minutes.
The first real chance of a try fell to the Scarlets, whose centre partnership of Jonathan Davies and King sent Morgan Stoddart on a searching run up the left touchline before he was tackled into touch 10 metres out by Fergus McFadden.
An offside decision against the Scarlets saw Leinster double their lead on 18 minutes with a second Contepomi penalty. It was a double blow for the Scarlets who then lost King a minute later.
The setbacks came thick and fast for the home side who conceded two converted tries in the space of three minutes. First Nacewa finished off a sweeping move down the left after the Scarlets lost ball in the Irish side's 22.
And Leinster's lead was stretched to 20-0 when Priestland's clearance kick was charged down by Girvan Dempsey and Jowitt was on hand to pick up and go over.
It took until 30 minutes for the Scarlets to register on the scoreboard when Priestland made some amends by kicking a penalty goal.
The Scarlets comeback continued when two minutes later Martin Roberts zipped in from 10 metres out for a converted try to halve the Leinster lead.
But five minutes before half-time Leinster hit back with a third penalty goal to give them a 23-10 interval lead.
At the start of the second half Priestland missed two kickable penalties in the space of two minutes.
And more points when begging when Gavin Evans ignored an overlap outside him as the Scarlets' hopes of a comeback faltered.
The Scarlets finally went in for their first try when Manu squeezed over with the Priestland conversion making it 23-17 after 53 minutes.
But Leinster hit back just after the hour mark with an unconverted try and a penalty. Jennings crossed to finish off a long-range effort. And though Contepomi missed the conversion he was on target with his fourth penalty to give the visitors a 14-point advantage.
After 69 minutes Contepomi was shown a yellow card for a professional foul.
The Scarlets thought they had grabbed a try back when Jonathan Davies went in at the left corner but the try was disallowed for a foot in touch by the television match official Tony Rowlands.
