Two Scarlets don't make the fitness race this week - centre Jonathan Davies (ankle sprain) and hooker Ken Owens (arm) missing out.
Scarlets Head Coach, Nigel Davies: "This game will be about who turns up hungrier on the day, the form leading up to it doesn't always count for much - it will probably rest on a couple of key moments, who gets them right and who takes their chances. It's going to be a tough match, it's a massive game in its own right and both teams understand that."
"It's one of the big games people want to come and watch and rightly so - the intensity it generates, the rivalry is huge and the respect is there between the two sides. These games always have an extra edge."
Scarlets: Daniel Evans, George North, Regan King, Gareth Maule, Sean Lamont, Stephen Jones, Tavis Knoyle, Iestyn Thomas, Matthew Rees (capt), Deacon Manu, Lou Reed, Dominic Day, Josh Turnbull, Johnathan Edwards, David Lyons.
Replacements: Emyr Phillips, Phil John, Rhys Thomas, Jonny Fa'amatuainu, Rob McCusker, Martin Roberts, Scott Williams, Rhys Priestland.
Ospreys 15 Lee Byrne 14 Richard Fussell 13 Tommy Bowe 12 Andrew Bishop 11 Shane Williams10 Dan Biggar 9 Mike Phillips 1 Paul James 2 Richard Hibbard 3 Adam Jones 4 Ian Gough 5 Alun Wyn Jones (Capt) 6 Jerry Collins 7 Marty Holah 8 Jonathan Thomas.
Replacements 16 Huw Bennett 17 Ryan Bevington?18 Craig Mitchell 19 Ryan Jones 20 Justin Tipuric 21 Jamie Nutbrown 22 James Hook 23 Nikki Walker