It will be the first time the local rivals have met at Llanelli's stunning new £23m Parc y Scarlets where the ticket office today (Thursday) reported advance sales of 10,000.
Scarlets head coach Nigel Davies, planning to bounce back from an April 4 home defeat to Glasgow, said: "The past two weeks have been tough for our coaches and players. Coming off our performance here against Glasgow it couldn't have been anything but.
"That performance was unacceptable - we all know that - and, as a result, much time has been spent getting to the bottom of a number of issues. These have ranged from our coaching to individual player performance and to our team structures.
"We have had to be very honest with each other in order to move on from that defeat and some moments have been pretty bruising."
Having lost painfully themselves last weekend against Munster in the Heineken Cup, the Ospreys will also have been taking a close look at themselves this week.
Davies said: "Munster are a very good team and, in fairness to the Ospreys, the visitors to Thomond Park were very much still in the game going into the second half until a couple of key moments when things didn't go for them.
"On Saturday, our two teams will be desperate to give our supporters something to shout about and, if there's one game with which we can both redeem ourselves somewhat, it's this one."
Davies has named former Osprey Martin Roberts at scrum-half with fellow Wales international Stephen Jones partnering him at fly-half and taking the captain's role in place of injured skipper Simon Easterby (knee).
Other internationals in the home line-up include wing Mark Jones, hooker Matthew Rees, lock Vernon Cooper, flanker Dafydd James and No 8 David Lyons. Young talent on show includes full-back Rhys Priestland, centre Jon Davies and flanker Josh Turnbull.
Centre Rob Higgitt is named on the bench having recovered from an ankle injury that has kept him out since November 1.
v Ospreys, Magners League, Parc y Scarlets, Sat Apr 18, 5.30pm
15 Rhys Priestland, 14 Mark Jones, 13 Jon Davies, 12 Gavin Evans, 11 Daniel Evans, 10 Stephen Jones (c), 9 Martin Roberts, 1 Phil John, 2 Matthew Rees, 3 Deacon Manu, 4 Vernon Cooper, 5 Dominic Day, 6 Josh Turnbull, 7 Dafydd Jones, 8 David Lyons. Reps - 16 Iestyn Thomas, 17 Mahonri Schwalger, 18 Aaron Shingler, 19 Rob McCusker, 20 Gavin Cattle, 21 Lee Williams, 22 Rob Higgitt.