Commenting on Friday's crucial fixture, Ulster head coach Brian McLaughlin said: "It is going to be an exceptionally tough game, the Scarlets at their home ground in the Magners League. It doesn't matter who you play at this stage, all these games are tough to win.
"We are playing at the Parc y Scarlets, we were there a couple of weeks ago with the Ravens, so we know what to expect.
"It's going to be a hard match, they will make us fight for every blade of grass. We have got to play out of our socks and be mentally prepared, if we are going to come away with the win which we really need."
The versatile Dan Tuohy moves to blindside flanker, while Ryan Caldwell comes in to partner Ed O'Donoghue in the province's second row.
Number 8 Chris Henry will once again captain the team, with Fijian flyer Timoci Nagusa drafted in as the only change to the backs division.
ULSTER (v Scarlets): Jamie Smith; Timoci Nagusa, Darren Cave, Paddy Wallace, Andrew Trimble; Ian Humphreys, Isaac Boss; Tom Court, Nigel Brady, BJ Botha, Ed O'Donoghue, Ryan Caldwell, Dan Tuohy, David Pollock, Chris Henry (capt).
Replacements: Andi Kyriacou, Bryan Young, Robbie Diack, Willie Faloon, Paul Marshall, Niall O'Connor, Simon Danielli.