With one round left of the regular BKT United Rugby Championship season to play Munster, Leinster and Ulster have secured play-off rugby, while Connacht remain in with a mathematical chance of extending their season into June.
Graham Rowntree and Leo Cullen's side are also clear of fifth-place Stormers and therefore guaranteed a home quarter-final.
Ulster’s victory over Leinster, and results elsewhere, meant they cannot finish worse than eighth in the table.
Those three now jostle for position and higher seedings, while Connacht have to claim five more points and hope results elsewhere fall their way.
Here’s what all the provinces need ahead of round 18, with 11 teams in total still in the play-off race.
Munster
The defending champions, off a run of eight straight wins, are in pole position heading into the final round.
Graham Rowntree’s side are top on 63 points, two clear of Bulls and three ahead of both Leinster and Glasgow.
A win of any hue when they host Ulster in Thomond Park on 1 June would assure top spot and home advantage for a potential semi-final and final.
A draw without a try bonus would mean they could be overtaken by all three chasers if they all won.
The first separating criteria when teams finish level on points is matches won and the top four all have 12 victories to this point.
A draw with a bonus point, for four tries, would leave them vulnerable to a Bulls win away to the Sharks.
Defeat, with or without a losing bonus point, could see them drop as low as fourth.
Leinster
Leinster’s third defeat in four games, against Ulster on Saturday, leaves them in third place and hoping that Munster and Bulls slip up.
The eight-time winners have 60 points and a five-point haul when they host Connacht could see them yet top the table if Munster were to take less than three points from their game at home to Ulster.
Leinster, themselves, could be overtaken by fourth-placed Glasgow if the Scots take five points from their home clash with bottom of the table Zebre and make up a 24-point (plus whatever margin Leinster might beat Connacht by) difference.
Ulster
Ahead of last weekend, Ulster needed six points to be assured of making the play-offs but results elsewhere meant that the four they secured in victory over Leinster were enough.
They are currently in sixth on 53 points, one behind Stormers and four ahead of both Edinburgh and Benetton, who face off in Treviso in round 18.
Should Stormers beat Lions at home then not even a win for Ulster against Munster in Thomond Park will improve their seeding but if the Cape Town side slip up then a win, or even a draw, could see Richie Murphy’s men up to fifth and, as it stands, facing a trip to Glasgow for their quarter-final.
If there is no movement in the top eight, they will return to Dublin to face Leinster at Aviva Stadium.
Defeat in Limerick, with or without a single bonus point would mean one of Edinburgh or Benetton could overtake Ulster with a five or four-point victory.
Connacht
Connacht, in tenth place on 45 points, are technically still in the race but they must beat Leinster, in a Friday night clash at the RDS, and earn a winning bonus point to stay in the mix ahead of the rest of the games on the Saturday.
Anything less and their season is over.
Their fingers are crossed, firstly, for a Lions defeat away to Stormers in which the Johannesburg team, on 49 points, fail to pick up a bonus point.
Even that haul is not likely to be enough with Pete Wilkins’ side needing the loser from the Benetton-Edinburgh match also to fail to pick up a losing bonus point.
Should either do so then it’s game over for the Westerners.
Meanwhile, in the most unlikely scenario, there remains a possibility that only the top six teams in the final standings would qualify for the Champions Cup next season.
If Sharks win the Challenge Cup on Friday against Gloucester they would qualify, while in the event that the team who finishes eighth in the table - for example Connacht - wins the tournament outright then they would also go forward as one of the URC's eight representatives in the Champions Cup.
Watch highlights of the weekend's action on Against the Head, 8pm Monday, RTÉ2 and RTÉ Player
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