Centre Luke Marshall returns to inside centre as Stuart Olding and Stuart McCloskey are ruled out with injury.
It's back to the big time for the Ireland international as coach Neil Doak plumps for three changes from last week.
Tight-head Declan Fitzpatrick and flanker Clive Ross complete the trio because Wiehahn Herbst and Nick Williams have been hamstrung.
The under-rated Dan Tuohy has been missed for his physicality.
Darren Cave has been showing all the arrows in his arsenal to more than fill the hole left by Jared Payne. Ulster will have to bring Tommy Bowe and Craig Gilroy into the game early and often to rack up the four tries they are necessary.
As always, scrum-half Ruan Pienaar will be pivotal to taking the points with captain Rory Best looking to put the squeeze on an improving Scarlets pack.
This will take some doing as tight-head Samson Lee did his fair share of damage for Wales in November and Jake Ball made his mark too.
Scarlets: L Williams; K Phillips, R King, S Williams (capt), M Tagicakibau; R Priestland, R Williams; R Evans, E Phillips, S Lee, J Ball, J Snyman, A Shingler, J Davies, R McCusker.
Ulster: L Ludik; T Bowe, D Cave, L Marshall, C Gilroy; I Humphreys, R Pienaar; C Black, R Best (capt), D Fitzpatrick, D Tuohy, F van der Merwe, R Diack, C Ross, R Wilson.