Both teams have performed well with two wins out of two in their European excursions and must now be looking to bring that form to bear in the Magners League to lift them from the wrong end of the table.
The Scarlets have the better record, having lost just once in the teams' last six meetings.
Elsewhere on Friday night, the Ospreys host Glasgow Warriors at the Liberty Stadium.
The result of this game is crucial to each team's prospects of finishing the round in the play-off zone - Glasgow currently hold fourth place, but a loss to the Ospreys would see their opponents leapfrog ahead of them.
In the 'Halloween Thriller' in Dublin on Saturday night, Leinster welcome Cardiff Blues to the RDS, a ground where the hosts have won their last eight Magners League games since a Munster success in September 2008.
In addition, the Blues have not tasted victory in Dublin since 2004.
Also on Saturday, top-of-the-table Ulster face defending Magners League champions Munster at Thomond Park Stadium.
The Munstermen have a formidable home record but Ulster will be looking for a third straight away victory to keep their spot at the top of the pile, their hosts will be hoping to reclaim a place in the top four.
In the final game of the round, Edinburgh and the Newport Gwent Dragons face off at Murrayfield on Sunday.
Edinburgh have a good record at the home of Scottish Rugby, the Dragons are not impressive on the road - facts reflected last season when each team won their home game.
MAGNERS LEAGUE - ROUND 7 FIXTURES:
Friday, October 30 -
CONNACHT v Scarlets, The Sportsground, 6.30pm
Ospreys v Glasgow Warriors, Liberty Stadium, 7.05pm (live BBC Wales/Setanta Sports Ireland)
Saturday, October 31 -
MUNSTER v ULSTER, Thomond Park Stadium, 5pm (live Setanta Sports Ireland)
LEINSTER v Cardiff Blues, The RDS, 6.30pm (live Setanta Sports 1/S4C)
Sunday, November 1 -
Edinburgh v Newport Gwent Dragons, Murrayfield, 5.05pm (live S4C/Setanta Sports Ireland)