The Scarlets have produced a winning formula at home this season taking victories and a draw in eight of their 11 home games this season - but they now face a close to full strength Ulster side, that will be frustrated with their one-point loss against the Ospreys last weekend.
Back into the Scarlets starting line-up comes new Wales caps Rhys Priestland and Josh Turnbull (back row) with Rob McCusker released by Wales and Sean Lamont by Scotland.
Scarlets Head Coach Nigel Davies said: "The spirit amongst the group this week has been really positive, there's been a buzz around training at Parc y Scarlets with the added energy of some of boys who have been on international duty coming back.
"The players are eager to push on and add to the good work they have done in the league so far this season. We have made it a priority and focus and the boys returning to the Scarlets jersey tomorrow night will want to show the added confidence they've had from being in their international camps in the past few weeks. It's been really obvious how eager they are to get out and play back here this weekend.
"We know Ulster will be at pretty much at full strength and with a number of returning Irish squad members as well, will be throwing everything at this game. The league competition is very tight at the top end of the Magners and they play-off ambitions like us and will be keen to knock us back.
"We have to target our home games, we've said that all season and our form here has improved from last season. These next two games are key to our ambitions in the league. It's a huge month for us, if we can get some results now in these next three games, it will go a long way to deciding whether we are in with a chance of a play-off place."
Scarlets: Daniel Evans, Gareth Maule, Regan King, Scott Williams, Sean Lamont, Rhys Priestland, Martin Roberts, Iestyn Thomas (capt), Emyr Phillips, Rhys Thomas, Vernon Cooper, Lou Reed, Rob McCusker, Josh Turnbull, Ben Morgan.
Replacements: Rhys Lawrence, Rhodri Jones, Simon Gardiner, Jonny Fa'amatuainu, Johnathan Edwards, Tavis Knoyle, Dan Newton, Joe Ajuwa.