Elsewhere on Friday night, former leaders Glasgow Warriors visit the Sportsground to play Connacht.
The Warriors will set a new record if they triumph in Galway as they have never before gone undefeated in five successive away league games.
There is just one game on Saturday. The focus once again turns to Wales, this time to Rodney Parade where the Newport Gwent Dragons host current Magners League champions Munster.
Having been in or around the play-off zone most of the season, Munster currently lie in fourth - just three points short of the leaders - an ideal place from which to make a challenge for top spot as the season draws towards its finale.
The round wraps up with two games on Sunday afternoon, Edinburgh v Ospreys and Cardiff Blues v Leinster.
The table-topping Ospreys, who took over the lead for the first time this season after their victory against Connacht in the last game of round 12, will have to complete a season's double over their hosts if they are to claim the win and retain their pole position.
Cardiff pulled off perhaps the surprise result of the last round, putting an end to their disappointing record against Glasgow Warriors by defeating the then leaders 30-7.
MAGNERS LEAGUE - ROUND 13 FIXTURES:
Friday, March 5 -
Scarlets v ULSTER, Parc y Scarlets, 7.05pm (live Setanta Sports Ireland/BBC Wales)
CONNACHT v Glasgow Warriors, the Sportsground, 8pm (live Setanta Sports 1)
Saturday, March 6 -
Newport Gwent Dragons v MUNSTER, Rodney Parade, 6.30pm (live Setanta Sports 1/S4C)
Sunday, March 7 -
Edinburgh v Ospreys, Murrayfield, 2pm (live S4C)
Cardiff Blues v LEINSTER, Cardiff City Stadium, 4pm (live Setanta Sports Ireland/BBC Wales)