Anything less than three match points from their Friday night derby against the Ospreys will see them drop out of contention, and depending on other results even a victory may not be enough.
Their opponents, the Ospreys, on the other hand will be looking for a win to reinforce their place in the top four and stay on course to retain the title.
Also on Friday, the Cardiff Blues, who are just outside the play-off zone but have a game in hand over all the teams above them, travel to Galway to face Connacht.
Eric Elwood's men will be looking to maintain their best ever league run which has seen them record five straight home wins, in the hope of achieving their highest ever finish in the competition.
There are two vital fixtures on Saturday - firstly, top of the table Munster could secure a home semi-final with a victory over the Scarlets, who themselves need the win to keep their chances of making the top four alive.
Then, the weekend wraps up with the perhaps the pick of the round as fourth-placed Leinster entertain second in the table Ulster at the RDS.
Both provinces were in Heineken Cup action last weekend, but with differing results. Ulster not only have to overcome their disappointment at their exit from that competition, but also an impressive home record that has seen Leinster win their last 24 regular season home games in Dublin.
Another home triumph is required if Leinster are to avenge the one game they lost at the venue - last season's grand final.
By the end of this round, we may have a much clearer picture of who is still in contention to carry off the Magners League title this year.
MAGNERS LEAGUE - ROUND 20 FIXTURES:
Friday, April 15 -
Newport Gwent Dragons v Ospreys, Rodney Parade, 7.05pm (live BBC 2 Wales)
CONNACHT v Cardiff Blues, the Sportsground, 7.45pm (live TG4)
Edinburgh v Aironi Rugby, Murrayfield, 7.50pm (live BBC ALBA)
Saturday, April 16 -
Benetton Treviso v Glasgow Warriors, Stadio di Monigo, 3pm
Scarlets v MUNSTER, Parc y Scarlets, 6.15pm (live TG4/S4C)
LEINSTER v ULSTER, the RDS, 8pm (live RTE 2/BBC 2 Northern Ireland)