Scarlets director of rugby Gareth Jenkins, in his last game in charge before taking over the Wales side, has named Lee Byrne at full-back in the Test player's last game before moving to the Ospreys.
No.8 Alix Popham is banned because of the red card received against Glasgow last week, and he has been replaced by Jonathan Mills. Phil John comes in for Iestyn Thomas at prop.
Ulster have made one change, bringing in Paddy Wallace at centre, with Jonny Bell dropping to the bench. Full-back Bryn Cunningham will win his 100th cap for Ulster against the Scarlets.
Coach Mark McCall's team are level with Irish neighbours Leinster at the top of the League table, but have a superior points difference and a game in hand.
"To go to the Scarlets and beat them on their own turf would be a good way to win the league," Ulster backrower Neil Best admitted. "It's all in our own hands now."
The Scarlets, who lost 17-10 to Glasgow last Friday, lie seventh.
Scarlets: L Byrne; M Jones, M Watkins, R King, G Evans; C Evans, D Peel; P John, A Gravelle, C Dunlea, V Cooper (capt), H Louw, I Afeaki, D Jones, J Mills
Replacements: J Davies, M Rees, C Wyatt, J Edwards, L Williams, G Bowen, G Evans
Ulster: B Cunningham; T Bowe, A Trimble, P Wallace, A Maxwell; D Humphreys, I Boss; B Young, R Best, S Best (capt), J Harrison, M McCullough, N Best, S Ferris, R Wilson
Replacements: N Brady, J Fitzpatrick, R Caldwell, N McMillan, K Campbell, J Bell, T Howe
Referee: Graeme Hannah (Scotland)