The visitors dominated the third quarter, Barry Davies scoring their only try, but indiscipline cost them in the end as they allowed Rhys Priestland to slot over some late kicks to se cure victory.

It was the Ospreys who settled quickest, Biggar intelligently controlling the opening plays, mixing boot and hand up effectively as his team looked to silence the sell-out Parc Y Scarlets crowd early on.

However, a testing up and under from Rhys Priestland put Barry Davies under pressure, the Ospreys fullback knocking on as he competed with opposite number Liam Williams under the highball, the Scarlets man just unable to keep his hack through of the loose ball infield.

Play was brought back for the Scarlets scrum, and although the home forwards found themselves under intense pressure they managed to get the ball away, and following a typical barnstorming George North run up the wing, halted by Kahn Fotuali'i, an Ospreys offside allowed Priestland to open the scoring in the 11^th minute.

Minutes later, Tom Smith was penalised at a defensive lineout for taking the Scarlets jumper out in the air, and again Priestland made no mistake, taking the score to 6-0.

It was a typical, frenzied, derby stuff and the Ospreys almost struck back from a well worked lineout move. Justin Tipuric secured good ball, setting up Biggar to burst into the 22 before it was worked out wide where the visitors had an overlap, but Tommy Bowe was unable to gather Shane Williams' pass just five metres out.

With the rain falling it was making conditions underfoot difficult, while the ball handling skills of both teams was being tested to the limit. The Ospreys seemed to have the upper hand at the scrum, and it was after a Scarlets offence in that area that Biggar was able to notch the first points of the afternoon for his team with a penalty from the 10m line on 28 minutes.

The Scarlets came back strongly and Biggar had to show great awareness in defence juist a minute or so later to snuff out the danger as Aaron Shingler charged down a Fotuali'i clearance on the line. The danger wasn't over for the Ospreys though, as from the resulting scrum five Ben Morgan picked up at the base to drive forward, before Rhys Thomas drove over to score, Priestland adding the extras to put his team 10 points clear.

Priestland then made no mistake with a penalty some 35metres out after Paul James was penalised at the scrum, taking the score to 16-3 in the Scarlets favour with just two minutes left in the first half.

A quickly taken tap-penalty then saw the Ospreys retreating again, Barry Davies having to cover as Priestland chased his own grubber, Davies clearing to touch to bring the first half to an end.

HALF-TIME: SCARLETS 16 OSPREYS 3

The Ospreys needed a bright start to the second period and Biggar duly slotted over his second penalty just three minutes in after the Scarlets were pinged at a scrum just inside their own half.

Priestland was then guilty of holding on as he gathered Shane Williams's grubber on his own line under pressure from the wing and his skipper Tipuric as the Ospreys launched a swift counter attack after North was dispossessed in the tackle.

The visitors opted for a scrum instead of going for goal, and with the Scarlets going backwards, the home team found themselves penalised on two more occasions. On the third occasion, Fotuali'i gave Shane Williams quick ball, but he was unable to find his way through and the Scarlets won turnover ball to clear.

Although they had failed to find a way through, an offside decision against Sean Lamont then allowed Biggar to continue chipping away at the Scarlets lead.

The rain had stopped and some late afternoon winter sun was breaking through the clouds, and it proved a great omen for the Ospreys who responded by producing their best move of the afternoon, resulting in their first try of the day from former Scarlet Barry Davies.

It was a flowing move that saw them move the ball the full width of the pitch and back. The scoring pass came from Andrew Bishop, freeing Davies on his right who gathered at speed and slid over in the corner, the TMO confirmed the grounding for Nigel Owens. Biggar missed with what was a very difficult conversion attempt though, leaving the score at 16-14 to the Scarlets 15 minutes into the second half.

The Scarlets had a chance to respond almost immediately after Shane Williams was guilty of holding on but Priestland's effort fell several metres short. Just a few minutes later he was handed a much easier opportunity after a dangerous tackle by Bowe just a couple of metres outside the 22 and this time Priestland made no mistake, taking the Scarlets lead back up to five points.

More pressure from the home side led to another penalty, a metre closer to the line, after an illegal Ospreys hand in the ruck, Priestland taking his team eight points clear with 12 to play.

Matthew Morgan replaced Biggar and his first involvement was to go for goal from a central position 43metres out after a deliberate knock-on but his kick drifted to the right of the sticks.

The game was starting to get bogged down in midfield, the Ospreys frustrated as they looked to claw back the deficit once again, the Scarlets happy to see the game becoming stop-start with the clock rolling down. A penalty allowed Morgan to put it in the corner, and the pack rumbled forward, being brought down inches short. They patiently recycled but the Scarlets held firm to keep their line intact, winning turnover ball to enable them to clear.

Priestland spurned another chance in front of the posts as the Scarlets held firm to secure their first win over the Ospreys in four years, the visitors leaving without even a bonus point as consolation.