Leinster currently top the pile on 78 points but by the time Saturday's match against Edinburgh has finished, they could find themselves down in third place.
Glasgow Warriors are in second spot on 74 points but host Zebre knowing that a bonus point win - and what would be an eighth win in a row - will keep the pressure on.
And perhaps more importantly, it would secure a home play-off, keeping Munster, who are just a point behind, at bay.
Munster meanwhile, host Ulster - who have already tied up fourth spot - and they will be determined to secure maximum points to take advantage of any potential slip ups from Leinster or the Warriors.
The dates and times of semi-finals have been confirmed and the first will take place on Friday May 16 at 19:35 (BST) and the second at 19:00 (BST) on Saturday May 17.
If Leinster and Glasgow are at Home - the Glasgow match goes into the Friday slot and the Leinster match into the Saturday slot.
If Leinster and Munster are at Home - the Leinster match goes into the Friday slot and the Munster match into the Saturday slot.
If Glasgow and Munster are at Home - the Glasgow match goes into the Friday slot and the Munster match into the Saturday slot.
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