The Scarlets stayed in contention for a Pro12 play-off berth after beating the Ospreys 22-10 at Parc y Scarlets on Saturday.
Rhys Priestland kicked 12 points and set up a try as the Scarlets secured a superb triumph over the league leaders.
The home side dominated the opening period and went into the break with a deserved 14-3 lead through Liam Williams’ score and three Priestland penalties.
Dan Biggar had drawn the Swansea-based team level early in the match via an effort off the tee, but they couldn’t find a way back into the contest after the interval and John Barclay’s touchdown, allied by another Priestland three-pointer, sealed the victory.
Dan Evans went over late on for the Ospreys but they deservedly succumbed for just the third time in the league this seasoon.
Although the visitors’ European campaign has proven to be a disappointment in 2014/15, they have been the standout side domestically.
However, it was the hosts, a team that have struggled for consistency, who opened the brighter and took the lead through the boot of Priestland.
But they received a setback when Scott Williams was shown a controversial yellow card for a high tackle. With the Llanelli-based outfit down to 14 men, that allowed Biggar to level matters, but the visitors couldn’t build on that score.
Instead, Wayne Pivac’s men held out with relative comfort and then regained their advantage via their fly-half’s second three-pointer.
Priestland was in the action again when his smart break and off-load sent full-back Williams across the whitewash.
Although the Welsh international was awry with the conversion, he was successful from the tee late in the half to move the Scarlets 14-3 in front at the interval.
Ospreys’ boss Steve Tandy needed a response from his side in the second period, but the league leaders were caught cold when centre Williams broke through. He was stopped agonisingly short of the line but, instead of panicking, the ball was shifted left to Barclay who touched down.
Once again Priestland failed to add the extras but fortunately his team-mates were presenting him with other kicking opportunities and a fourth penalty was duly slotted after 55 minutes.
That effectively secured the win as, although the away team managed to get a score back through Evans, the Scarlets’ defence remained strong.
Tries: L Williams, Barclay
Pens: Priestland 4
Yellow Card: S Williams (10th minute)
Scarlets: 15 Liam Williams, 14 Hadleigh Parkes, 13 Regan King, 12 Scott Williams (c), 11 Michael Tagicakibau, 10 Rhys Priestland, 9 Aled Davies, 8 Rob McCusker, 7 John Barclay, 6 Aaron Shingler, 5 Johan Snyman, 4 Jake Ball, 3 Samson Lee, 2 Kirby Myhill, 1 Rob Evans.
Replacements: 16 Ryan Elias, 17 Wyn Jones, 18 Rhodri Jones, 19 George Earle, 20 Will Boyde, 21 Gareth Davies, 22 Steven Shingler, 23 Jordan Williams.
Ospreys: 15 Dan Evans, 14 Hanno Dirksen, 13 Ashley Beck, 12 Josh Matavesi, 11 Aisea Natoga, 10 Dan Biggar, 9 Rhys Webb, 8 Tyler Ardron, 7 Justin Tipuric, 6 Dan Lydiate, 5 Alun Wyn Jones (c), 4 James King, 3 Dmitri Arhip, 2 Scott Baldwin, 1 Marc Thomas.
Replacements: 16 Sam Parry, 17 Duncan Jones, 18 Aaron Jarvis, 19 Rynier Bernardo, 20 Sam Lewis, 21 Martin Roberts, 22 Sam Davies, 23 Tom Grabham.
Referee: John Lacey (Ireland)