Scarlets have named their side for the PRO12 clash with the Ospreys at Liberty Stadium on Boxing Day, with Jonathan Davies leading the region.
The hosts are facing quick turnaround from their battle on Friday at Cardiff Blues, while the Ospreys have had more rest time, not having played since their success over Toulouse.
Scarlets make four personnel changes to the starting XV that was victorious at the Arms Park with Aled Davies getting a start back at scrum-half; former Osprey Kristian Phillips comes onto the wing, Matthew Rees starts at hooker and Jake Ball comes in at lock alongside George Earle.
The Ospreys host the Scarlets with a strong home record behind them this season having been victorious in their last seven games at Liberty Stadium. The Ospreys have won their last five clashes with fellow Welsh regions.
"This game marks the start of a very busy month for the Ospreys and it's crucial that we perform consistently, putting in top level performances in every single game now so that we can push for a top four spot in the PRO12 and the knockouts in Europe," said Ospreys boss Steve Tandy.
"This is the type of game that everybody wants to be involved in so training has been full on this week, which is great when you are a coach. We've got three big games in nine days so the challenge for us is to make sure the team is properly prepared for each one, and that will mean making a few changes along the way to keep people fresh and to give us the best chance of getting the performance levels in that we'll need if we are going to get the result we want from these games.
"After Boxing Day we go to the Dragons and then we play Zebre at the Liberty on 4th January in another crucial home game and we know that we have to be at our very best for each game if we want to move into the top four and stay there.
"With the biggest crowd in two years already confirmed for Boxing Day we know that there's going to be a great atmosphere, which is fantastic. It'll be pretty special, we've got good memories of playing the Scarlets at Christmas at the Liberty and it's up to these boys to make their own history this week.
"We know that they'll come here confident after winning at the Blues last week, they are a very dangerous team so we will have to be at our best if we are going to send our supporters home with the best Christmas present they could ask for."
Ospreys: 15 Richard Fussell, 14 Ross Jones, 13 Andrew Bishop, 12 Ashley Beck, 11 Eli Walker, 10 Dan Biggar, 9 Kahn Fotuali'i (capt), 8 Joe Bearman, 7 Justin Tipuric, 6 Ryan Jones, 5 James King, 4 Ian Gough, 3 Adam Jones, 2 Richard Hibbard, 1 Ryan Bevington.
Replacements: 16 Scott Baldwin, 17 Duncan Jones, 18 Cai Griffiths, 19 Lloyd Peers, 20 Morgan Allen, 21 Rhys Webb, 22 Matthew Morgan, 23 Tom Isaacs.
Scarlets: 15 Liam Williams 14 George North, 13 Jonathan Davies (capt), 12 Scott Williams, 11 Kristian Phillips, 10 Aled Thomas, 9 Aled Davies, 8 Kieran Murphy, 7 Aaron Shingler, 6 Josh Turnbull, 5 George Earle, 4 Jake Ball, 3 Samson Lee, 2 Matthew Rees, 1 Phil John.
Replacements: 16 Emyr Phillips, 17 Shaun Hopkins, 18 Jacobie Adriaanse, 19 Sione Timani, 20 Rob McCusker, 21 Tavis Knoyle, 22 Gareth Owen, 23 Gareth Maule.
Date: Wednesday, December 26
Venue: Liberty Stadium
Referee: Nigel Owens (Wales)
Assistant Referees: Gwyn Morris (Wales), Jon Mason (Wales)
Television match official: Derek Bevan (Wales)
Citing Commissioner: Ray Wilton (Wales)