Scarlets head coach Wayne Pivac is urging his side to go back to basics if they are going to topple current GUINNESS PRO12 leaders Ospreys.

While Ospreys returned to the top of the GUINNESS PRO12 table with a 31-20 home win over Ulster, Scarlets slipped to defeat at Cardiff Blues for a second successive loss.

And the history books suggest that they could lose three in a row for the first time in a year since they have not won away from home in any competition since a trip to Treviso in February.

They have not upset a fellow Welsh region at their regular home ground since beating Blues at the Arms Park in December 2012.

Scarlets’ only victory over Ospreys in their last dozen encounters was 22-12 at Parc y Scarlets on Boxing Day 2011, whilst the only occasion they have ever been triumphant at Liberty Stadium came on September 11 2007.

In order to change this unwanted record Pivac has welcomed back a number of key frontline players to his starting XV with Scottish international John Barclay returning from a thigh haematoma that has kept him out of the side since the GUINNES PRO12 defeat to Connacht in November.

Barclay will lead the Scarlets at Liberty Stadium in captain Ken Owens (neck) and vice-captain Scott Williams' (shoulder sprain) absence.

Full-back Liam Williams has been cleared fit for duty after suffering a sprained ankle in the region's emphatic victory over Ulster in Europe a fortnight ago.

Former Auckland captain Hadleigh Parkes makes his first start for the region as he links up with fellow Kiwi Regan King, who made his 150th regional appearance in last weekend's derby against Cardiff Blues, in the centre.

Scrum-half Aled Davies will make his 50th appearance for the region as he is likely to face in-form international scrum-half Rhys Webb.

In the pack Jake Ball and George Earle link up in the second row with Aaron Shingler returning to fitness after an illness kept him out of last weekend's clash.

"The reason they're [Ospreys] at the top of the table is that they're very consistent and solid, they have some very good leaders within that team,” Pivac said.

"They execute the basics very well – something that we're not doing at the moment. This is probably the biggest difference in the two sides.

"We weren't happy with our game across the board really against the Blues, the scrum started slowly but got better as the game went on. We have some work to do this week to ensure we're disciplined across the 80 minutes.

"Everybody has talked about it since I've been here; everybody has been saying 'just wait until you get to the Ospreys game'. It's going to be exciting."

As for the Ospreys, Dan Lydiate makes his first start for the region after being handed the No.6 shirt, meaning James King moves to the second row in place of Rynier Bernardo.

Ospreys are unchanged among the backs as they go in search of a ninth straight GUINNESS PRO12 victory at the Liberty Stadium, with head coach Steve Tandy hoping to give the fans some late Christmas cheer.

“This is the big one as far as the supporters are concerned and it’s fantastic that there’s going to be the biggest crowd for two years at a regional rugby ground, keeping the Christmas derby tradition well and truly alive,” Tandy said.

“This is a derby that really impacts on people’s everyday lives, with family, friends and workmates supporting opposite sides and there’ll be a great atmosphere at the Liberty on Saturday.

“As far as we are concerned as a team, we have to take the passion created by a packed Liberty Stadium and channel it in the right direction. For us, it’s just the next game in a busy schedule and it’s crucial that we don’t allow the occasion to carry us away.

“We showed what we can do last weekend, we put in 50 or 60 good minutes against Ulster and got the rewards.

“What we have to do this Saturday is get that little bit better, that little bit sharper, and do it for 80 minutes. It’s important that we review where we go wrong and always keep striving to be better, and that’s been the focus this week.”

At Liberty Stadium, 5.15pm. Live on Sky Sports/S4C
Referee: Marius Mitrea (FIR, 34th competition game)
Assistant Referees: Wayne Davies, Jon Mason (both WRU)
Citing Commissioner: Jeff Mark (WRU)
TMO: Derek Bevan (WRU)