|Scarlets (9) 16|
|Tries: Owens Cons: Priestland Pens: Priestland 3|
|Cardiff Blues (3) 6|
|Pens: Patchell 2|
Scarlets are in pole position for the Pro12's final automatic European Champions Cup spot next season after a hard-fought win over Cardiff Blues.
The west Wales region climbed back above Connacht ahead of next Saturday's final regular season round.
Rhys Patchell gave Blues an early lead, but Rhys Priestland kicked 11 points on his final home Scarlets appearance before joining Bath next season.
Home hooker Ken Owens scored the game's decisive and only try.
Wayne Pivac will take his side to Treviso next weekend hoping for a high-scoring, bonus-point win.
Connacht will be looking to do likewise at the same time against Ospreys, who are chasing a home draw in the play-offs.
Edinburgh, who host Leinster, are also in the mix.
But no matter what the outcome of that shakedown, at least Priestland can look back on a winning end to his time in Llanelli.
Priestland heads to Bath having ended his 156th Scarlets game with a total of 1,095 points for them.
The pressure was all on the hosts in a home Welsh derby against the nation's poorest-performing region this season.
And maybe that showed as Scarlets lacked the early sense of adventure that needing a bonus-point win should perhaps have encouraged.
Blues' defence was often equal to the challenge in the opening period.
But at other times handling errors close to the visitors' line cost Scarlets the chance to go over, while Blues also failed to spark in attack.
The home side fell behind against the run of play to a Patchell penalty after Liam Williams was sin-binned for illegal work on the floor.
But by half-time Priestland had kicked Scarlets into a 9-3 lead as the Wales fly-half converted pressure into points.
Blues had lost full-back Gareth Anscombe, hooker and captain Matthew Rees and lock Jarrad Hoeata to injury by that point.
After that tight first half, the attacking high points began to flow after the break.
After Patchell had kicked Blues to within three points, his foot-race with Scott Williams and a searing break from home scrum-half Aled Davies underlined the threats each side possessed.
But those moments, like Priestland's chip and chase to the Blues posts, again ended in frustration for the attackers.
Worse still for Davies, his game ended in the collision that brought his run to an abrupt end with Rhodri Williams taking over.
Patchell slipping over as he attempted - and failed - to draw the Blues level with another penalty shot merely seemed to underline the nature of the contest thus far.
The home side eventually got it right as they abandoned hope of breaking the visitors' defence with ball in hand and instead chose the direct route from a close-range line-out.
Captain Owens was rewarded with the try as forwards and some backs combined to break Blues' resistance, and Priestland converted to seal victory.
Scarlets: Liam Williams; Harry Robinson, Hadleigh Parkes, Scott Williams, Steffan Evans; Rhys Priestland, Aled Davies; Phil John, Ken Owens (captain), Peter Edwards, Jake Ball, Lewis Rawlins, Aaron Shingler, James Davies, John Barclay.
Replacements: Ryan Elias, Rob Evans, Jacobie Adriaanse, George Earle, Rory Pitman, Rhodri Williams, Steven Shingler, Adam Warren
Cardiff Blues: Gareth Anscombe; Alex Cuthbert, Garyn Smith, Gavin Evans, Joaquin Tuculet; Rhys Patchell, Lloyd Williams; Thomas Davies, Matthew Rees (c), Craig Mitchell, Jarrad Hoeata, Filo Paulo, Josh Turnbull, Sam Warburton, Josh Navidi
Replacements: Rhys Williams, Sam Hobbs, Scott Andrews, Lou Reed, Manoa Vosawai, Tavis Knoyle, Tom Isaacs, Richard Smith
Referee: John Lacey (WRU)
Assistant Referees: Ben Whitehouse, Wayne Davies (both WRU)
Citing Commissioner: Gwyn Bowden (WRU)
TMO: Tim Hayes (WRU)