Neath-Swansea Ospreys make the short trip west anxious to stop a slump that has seen them crash from league leaders back in mid-October to their current 9th place.
Their 42-18 victory over Edinburgh Rugby on October 17 must seem a distant memory after four straight Celtic League defeats, at home to Connacht and Leinster Lions and away at The Borders and Cardiff Blues.
"A lot of people are making a great deal of this being a new local derby between teams who traditionally had major rivalries," said Llanelli Scarlets coach Nigel Davies.
"However, we are focusing on ourselves and what we have to try and achieve rather than the emotions of the occasion.
"We are expecting a major contest because, while they will be hurting from some of the criticism that has gone their way, we know they are a very good team."
The Scarlets players were given a four-day break over Christmas but it has been back to business with a vengeance this week.
"We have not played for a few weeks now so we have been focusing on key aspects of our game that we hope will give us a performance while also taking the opportunity to work on the conditioning of the players," said Davies.
"For one thing, we know we will have to have our set pieces right otherwise we will be in for a very difficult night.
"We expect it to be a pretty physical encounter with the Ospreys coming with a massive amount of attitude and commitment.
"I guess the Ospreys may themselves have been critical of their defence in a few recent games so we anticipate them being very stubborn in that department while they will probably have a crack at our line-out as well."
The Scarlets have rested seven of the Heineken Cup side that won at the Borders in their last outing. Mark Taylor, Stephen Jones, Adam Jones, Dwayne Peel, Robin McBryde, John Davies and Scott Quinnell drop out.
Davies - who has played every game for the Scarlets this season - is the only one not to find a spot on the bench. Canadian international Jon Thiel gets a first start for the Scarlets in Davies' absence, and there is a welcome return to fitness for Chris Wyatt.
Tal Selley, Gareth Bowen, Mike Phillips, Aled Gravelle and Dave Hodges are the other changes to the Scarlets side. Captain Leigh Davies is likely to be out for another three weeks with his ankle injury while Wales wing Mark Jones hopes to get a run in the Welsh Premiership for Llanelli at Aberavon on Saturday.
The Celtic League will go on the back burner for the following four weekends when the Heineken Cup and Parker Pen Challenge Cup take centre stage with Llanelli Scarlets facing back-to-back clashes with Agen followed by the return fixtures against The Borders and Northampton Saints.
"It is a demanding programme - but it is exactly what we want," said Davies. "These are all top quality games that we need to raise our standards."
The Scarlets hope that Wales wing Mark Jones will start easing his way back from knee trouble by playing for Llanelli against Aberavon in the Welsh Premiership this weekend but club captain and international centre Leigh Davies is still looking at around three more weeks out of action following his ankle injury.
The Ospreys have selected Wales wing Shane Williams at full-back in the continued absence of Gavin Henson. Elvis Sevalai'i comes in on the wing as the only change to the back-line that started against Edinburgh.
But coach Lyn Jones has shaken up the pack as his side bids to end a six match losing run with internationals Gareth Llewellyn and Gavin Thomas both dropping to the bench.
There has been some encouraging news for Jones in that Wales prop Duncan Jones, who broke his leg at the World Cup, is expected to return in time for their second Heineken Cup game against Toulouse on16 January. Fellow prop Paul James has undergone an operation on his back, but won't be fit again until the end of March.
"The last few weeks have been a testing time for everyone, but a lot of responsibility goes to the captain and leading players to pull things around," said Ospreys skipper Scott Gibbs.
"They are the arch enemy, this is a tribal event and we are looking forward to a highly physical encounter. Matches like this are the reason we play."
Llanelli Scarlets: B Davies; G Evans, T Selley, M Watkins, S Finau; G Bowen, M Phillips; I Thomas, A Gravelle, J Thiel, V Cooper (capt), C Wyatt, D Jones, S Easterby, D Hodges.
Replacements: P John, R McBryde, A Jones, S Quinnell, D Peel, S Jones, M Taylor.
Neath-Swansea Ospreys: S Williams; D Tiueti, E Sevalai'i, S Gibbs (capt), S Terblanche; S Connor, A Williams; A Millward, B Williams, A Jones, A Newman, J Thomas, J Bater, R Pugh, N Bonner-Evans.
Replacements: H Bennett, G Llewellyn, C Griffiths, G Thomas, M Jones, J Storey, G Morris.
Referee: Nigel Whitehouse (Gower)