The Ospreys are the best placed of the trio and currently lie in third position, just two points behind second placed Ulster.
In their final three games, the Swansea-based side face a Welsh derby this weekend away to the Dragons before hosting current league leaders Munster at the Liberty Stadium. The regular season concludes for Sean Holley's side with a trip to bottom-placed side Aironi.
Just a point separate the Blues and Scarlets in fifth and sixth place respectively. Leinster currently occupy the last play-off position, but with a game in hand on the teams around them, the Blues are well positioned ahead of the run-in.
On Friday they travel to the Sportsground to play Connacht and their three remaining fixture after that see Treviso travel to the Cardiff City Stadium and then away derby games against the Dragons and the Scarlets.
That final game of the season in Llanelli could be a winner takes all encounter as the Scarlets try to ensure they feature in the semi-final matches.
Nigel Davies' side begin their final three matches by hosting Munster in Llanelli on Saturday.
Then it is an away trip to the Warriors for the Scarlets before welcoming the Blues to the Parc y Scarlets on Saturday May 6.