Scarlets had beaten Leinster the previous day but the lack of a bonus-point try saw them slip back into second.
However, round five presents the Welsh region with the opportunity to return to the summit, should they record a ninth straight GUINNESS PRO12 win.
They come up against a confident Munster side, however, who have lost just once in their last 11 PRO12 outings - in last season's final - and an in-form fly-half in the shape of Ian Keatley.
Man-of-the-match against the Blues, Keatley grabbed a try and converted all five that day, edging him closer to Newport Gwent Dragons stand-off Jason Tovey in the race to be the GUINNESS PRO12's most accurate marksman from the tee.
Elsewhere on Friday, the RDS will host a re-match of the 2014 PRO12 Final - at the same setting and live on Sky Sports - when Leinster host Glasgow Warriors.
The Leinstermen have lost just once at the RDS in their last 33 matches in all competitions, while the Warriors come into the clash off the back of a five-point victory over the Dragons.
And if Ian Madigan - fresh from a Rugby World Cup quarter-final defeat with Ireland - features for the hosts, it will be his 100th GUINNESS PRO12 appearance.
Another man hoping to bring up a century of appearances in the competition is Aled Brew when the Dragons host winless Benetton Treviso.
Indeed, the Italian outfit have slipped to 11 straight GUINNESS PRO12 defeats, though three bonus points keep them off the bottom of the table.
Zebre occupy that spot after a 34-15 defeat at Connacht last Friday - their tenth league reversal in a row - but they have beaten Saturday's opponents Edinburgh twice before.
However, this is an Edinburgh side on form, having made their best ever start to a GUINNESS PRO12 season with a four wins in as many games.
Connacht are level on points with Edinburgh, despite having lost once this season, after picking up their third try bonus point of the campaign against Zebre.
They achieved that with four tries inside 40 minutes - no team has managed it quicker so far this season - but Pat Lam's side can expect a tougher test this weekend.
They visit an Ospreys side fresh from their first win of the campaign and knowing Connacht have only beaten the Welsh outfit once in their last 14 encounters.
Finally, Cardiff Blues visit an Ulster side with a formidable home record, unbeaten in their last 13 GUINNESS PRO12 outings at the Kingspan Stadium.
Should they lose it will complete a clean sweep of defeats away to the four Irish provinces in the opening five rounds of the season.
They do, however, boast the competition's top try-scorer - Josh Turnbull with four - and top point-scorer, in the shape of Rhys Patchell (53).
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Guinness PRO12 Zebre News
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