The collision of the four semi-finalists means, amidst a multitude of other possibilities, that any of them could be top of the pile, all within 24 hours.
Ospreys, fourth on 66 points, put their unbeaten home record at the Liberty Stadium on the line against the Warriors, first on 70, on Friday night. Ulster, third on 67, do the same against Munster, second on 68, in the Kingspan Stadium on Saturday afternoon.
The permutations would have tested Archimedes and his fellow mathematicians of ancient Greece. What can be said without fear of contradiction is that a Warriors victory in Swansea would guarantee Gregor Townsend's team the priceless reward of a home semi-final in the play-offs later this month.
They are the only one of the twelve not to have gained a solitary losing bonus point all season, largely on account of the fact that they have been doing a lot of winning.
But…what if both Ospreys and Ulster were to lose their unbeaten home records? In that event Munster would be virtually home and dry for a semi-final at Thomond Park.
What if Ospreys and Ulster finish the regular season with the customary home win? The Welsh region would replace the Warriors at the top of the table only to be replaced in turn by Ulster, a scenario which would shove the current top two (Warriors and Munster) out of home semi-final territory.
The Warriors may have set the pace virtually from the start but they know that all the good work done throughout the season could be undone if they come a cropper at the penultimate hurdle. Should that come to pass their final fixture of the regular season, Ulster at Scotstoun, will assume still greater importance.
Ospreys have won nine and drawn one of their ten home games, an unbeaten PRO12 run stretching all the way back to February of last year when Munster beat them 25-11.
Ulster meet their old inter-provincial rivals reinforced by a perfect ten-out-of-ten at home, a sequence of invincibility matched only by the Warriors on Clydeside. Ruan Pienaar and company have not lost a PRO12 match in Belfast since Leinster edged them out 22-20 this time last year.
All four contenders have been collecting bonus-point victories on a regular basis in recent weeks, an illustration of their willingness to bust the proverbial gut for the distinction of succeeding Leinster as PRO12 champions. Two of them will fall behind this weekend, always assuming that neither match ends in a draw.
The current form of the top four over their last five outings shows how they have all raised their game, like marathon men pushing the accelerator in readiness for the final lap of a severe endurance test through autumn, winter and into spring.
Ospreys: 21 points out of 25 - beat Cardiff Blues (a), Benetton Treviso (a), Zebre (h), Munster (h), drew with Leinster (h).
Munster: 20 points out of 25 - beat Benetton Treviso (h), Edinburgh (a), Connacht (h), lost to Ospreys (a), beat Glasgow (h).
Ulster: 19 points out of 25 - beat Leinster (h), Connacht (a), Cardiff Blues (h), lost to Newport Gwent Dragons (a), beat Scarlets (h).
Warriors - 18 points out of 25 - beat Connacht (a), Cardiff Blues (h), drew with Leinster (a), beat Zebre (h), lost to Munster (a).
The final round on May 16 sees two of the four in Ireland - Munster at home to the Dragons, Ospreys in Galway against Connacht. The other fixture - Warriors against Ulster in Glasgow - could conceivably be a dress rehearsal for the Final in Belfast on May 30 or, there again, it could be nothing of the sort.
In the not unlikely event of two or more teams finishing level on match points, the final pecking order will be determined by the number of matches won - where Glasgow have 15 and the other 3 teams have 14, then the difference between points for and against over the season. Munster have the advantage in that respect at +191 with the rest running neck-and-neck - Ulster +174, Ospreys +173, Warriors +169. Still all square after that and we're looking at tries scored, most points scored, difference in tries scored, fewest number of red cards and finally the fewest number of yellow cards received !
The other race, the one to secure sixth place and with it the last guaranteed spot in next season's European Champions' Cup, is not quite as congested but hardly much less intriguing. The Scarlets lead the chase but by the narrowest possible margin, a point ahead of Edinburgh and five clear of the other challenger, Connacht.
Edinburgh must forget about what might have been after pushing Gloucester all the way during last week's Challenge Cup final, a gallant attempt which left them a converted try short of winning Scotland's first European trophy.
They will have no margin of error at Rodney Parade on Friday night against the Dragons whom they subjected to a five-try beating at BT Murrayfield in the Challenge Cup semi-final three weeks earlier.
A win would push Alan Solomons' team into sixth place above the Scarlets if only for a matter of hours before the West Walians' home fixture against the Blues on Saturday afternoon. Wales' capital region, in the throes of drawing up a short-list to succeed Mark Hammett as head coach, have won only twice on the road all season - at Zebre in early September and at the Dragons on New Year's Day.
Connacht, their Champions' Cup ambitions damaged by a run of four straight defeats, must win their two remaining matches, Zebre away on Saturday and Ospreys at home the following Saturday, and then hope other results go their way.
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