The Scarlets travel in positive and focused mood with an impressive backline ready to fire - having fine-tuned their performance after the home win against Treviso on Sunday.
The Scarlets narrowly lost out to Ulster in the final minutes of a hotly contested game at Parc y Scarlets in February, and the frustration of that loss (18-16) in the dying seconds is something the Scarlets will be looking to put this right. Ulster have never managed to achieve a season's double over Scarlets.
Wing Sean Lamont (hamstring strain), scrum-half Gareth Davies (dead leg) and wing George North (minor concussion) do not make late fitness tests but back and on the bench comes Wallaby no8 star David Lyons after injury.
Wales and Scarlets captain, British Lions hooker Matthew Rees back at the helm again as captain said: "We put ourselves in a great position at the beginning of the season, we have played well in our home games - we made a statement and put ourselves in a very good position.
"A couple of games recently haven't gone our way but now we have to concentrate on the remainder of the season. It's a tough ask to get a result out there, but we have our best team out and we know Ulster will also be looking forward to a Heineken Cup quarter final.
"It's in our hands - we have to win our four remaining games starting with Friday night. We're in a dog-fight now with the other teams around us. We got the victory against Treviso last weekend, it wasn't the best of games but we have put things right this week.
"The conditions out there are going to be tricky, it will be an arm wrestle early on and we have to take the game to them. It all starts up front and delivering a set-piece for our backline to play off - and we know we've got some great players in our backline."
Scarlets: Rhys Priestland, Gareth Maule, Regan King, Jon Davies, Morgan Stoddart, Stephen Jones, Tavis Knoyle, Iestyn Thomas, Matthew Rees (capt), Rhys Thomas, Lou Reed, Rob McCusker, Josh Turnbull, Johnathan Edwards, Ben Morgan.
Replacements: Emyr Phillips, Rhodri Jones, Peter Edwards, Aaron Shingler, David Lyons, Martin Roberts, Daniel Evans, Scott Williams.
Ulster: A D'Arcy; A Trimble, N Spence, P Wallace, S Danielli; I Humphreys, R Pienaar; T Court, R Best, BJ Botha, J Muller (capt), D Tuohy, R Diack, W Faloon, P Wannenburg.
Replacements (16-23): A Kyriacou, P McAllister, D Fitzpatrick, T Barker, C Henry, P Marshall, I Whitten, C Gilroy.