With only two points separating the top three sides, a loss for any of them could end their dreams of hoisting the sought-after trophy in the middle of May.
This Friday night at Stradey Park, the Scarlets, desperate to erase the memories of last weekend's Heineken Cup quarter-final loss to Biarritz Olympique host the Leinster Lions whileUlster host fellow Irish province Connacht. On Saturday, The Dragons put their unbeaten League home record on the line when they welcome the Cardiff Blues to Rodney Parade in a crucial game for both sides.
And the excitement isn't just centred on the race for the title. With Heineken Cup spots up for grabs among the Welsh and Scottish sides, things are getting tight at the other end of the table. The bottom-placed side from both Wales and Scotland lose their place in Europe's top tournament next season, and the heat is going on several teams with only four matches left to play.
The Blues are holding down the fifth Welsh position - they are currently the ones in most danger of failing to qualify for the 2004/2005 Heineken Cup - with 42 points, but have the Neath-Swansea Ospreys (45) in their sights, while the Celtic Warriors (48) are having a nervous look over their shoulders.The Blues have the daunting task of getting four points at Rodney Parade - which has proved beyond any Celtic team this season - while the Ospreys host bottom-placed The Borders and will be gunning for the full five points.
In the other game, defending champions Munster take on the leading Scottish side and Heineken Cup quarter-finalists Edinburgh Rugby at Musgrave Park as they build towards a mouth-watering Heineken Cup semi-final against London Wasps.
Of the front runners for the title - and now it's down to the top three - Ulster look to have the easiest task. They have the home advantage and a full deck to choose from against a Connacht side who may see fit to give some of their bigger names a rest ahead of the crucial Challenge Cup semi-final seeond leg a week later.
Second placed Llanelli Scarlets on the other hand face a Leinster Lions side that will have a totally different look to it from recent months with Girvan Dempsey, Shane Horgan, Gordon D'Arcy, Brian O'Driscoll, Reggie Corrigan, Shane Byrne and Malcolm O'Kelly all returning to the fold. If the Scarlets are suffering any hangover from their Heineken Cup demise, they needn't expect this Leinster side provide them with the 'hair of the dog.'
Third placed Gwent Dragons face a Cardiff outfit who have cast off their early apathetic form and with a Heineken Cup place on offer this could prove the Dragons' toughest home test to date.
Outside of this the main interest centres on which Scottish side will fail to make the cut from this competition for next year's Heineken Cup.
Strangely enough, even though they face Munster in Musgrave Park, Edinburgh might just improve their position after Friday nights matches.
They will likely face a home side whose big stars will be in the stands - with the noise of Wasps buzzing in their ears - while their compatriots, Glasgow entertain Celtic Warriors and Borders travel to Neath-Swansea Ospreys where the most they can hope for is a blast of good healthy sea air.
Ulster: Bryn Cunningham; Scott Young, Seamus Mallon, Paul Steinmetz, Tommy Bowe; David Humphreys, Kieran Campbell; Ronan McCormack, Paul Shields, Simon Best; Gary Longwell, Rowan Frost; Andy Ward capt, Neil McMillan, Roger Wilson. Replacements: Nigel Brady, Rod Moore, Tim Barker, Neil Best, Neil Doak, Paddy Wallace, James Topping.
Leinster: Girvan Dempsey; Shane Horgan, Gordon D'Arcy, Brian O'Driscoll, Brendan Burke; Felipe Contepomi, Brian O'Riordan; Reggie Corrigan capt, Shane Byrne, Peter Coyle; Malcolm O'Kelly, Ben Gissing; Victor Costello, Niall Ronan, Des Dillon. Replacements: Emmett Byrne, Gavin Hickie, Leo Cullen, Aidan McCullen, Brian O'Meara, David Quinlan, John McWeeney.
Referee: Malcolm Changeleng (Scotland).