There is now a real log jam for the top four places, with just seven points separating the second-placed side, Munster, from the Blues in seventh, with just 25 possible points still to play for this season.
The headline game this round must be Leinster's encounter with the Ospreys at the RDS on Friday night. Joe Schmidt's men have comfortably led the table since round 10.
But the Ospreys must know that a victory, other results permitting, could see them regain second spot, while defeat could see them drop out of the top four placings altogether.
The other stand-out fixture this round is Cardiff's derby clash with the Scarlets. Both regions are just outside the play-off zone on 45 points, victory not only secures the points for the winning team, but denies their opponents the opportunity to ad to their tally.
The same four teams have occupied the play-off positions since round 8. Although their placings may have changed, will the same four still be there when round 18 wraps up this weekend?
RABODIRECT PRO12 - ROUND 18 FIXTURES:
Friday, March 23 -
LEINSTER v Ospreys, the RDS, 7.05pm (live RTÉ Two/BBC 2 Wales)
Edinburgh v Newport Gwent Dragons, Murrayfield, 7.30pm
Glasgow Warriors v Aironi Rugby, Firhill Stadium, 7.35pm (live BBC ALBA)
Saturday, March 24 -
Benetton Treviso v ULSTER, Stadio di Monigo, 4.15pm local time/3.15pm Irish time (Rai Sport 2/BBC Northern Ireland red button)
Cardiff Blues v Scarlets, Cardiff City Stadium, 6.30pm (live S4C)
CONNACHT v MUNSTER, the Sportsground, 7.45pm (live TG4)