Ulster arrive at Leinster's RDS on Saturday desperate to spoil Brian O'Driscoll's Dublin farewell party and reach the PRO12 final.
Inter-provincial derbies always make for special occasions in Ireland: the partisan passion and fervour from the stands, the calibre of player on show, the fierce rivalries and the clout they boast when the time comes for the Ireland head coach to make his selections combine to create a wonderful rugby concoction.
With the nation's big three, Leinster, Munster and Ulster perennial challengers for the PRO12 title, drawing huge domestic crowds and top players, there is always plenty of spice.
So with three brilliant servants not just to their provinces, but to the sport of rugby potentially saying their farewells to the game this Saturday, this RDS encounter has more to it than most.
There are few adjectives left on the shelves that do O'Driscoll's contribution to Leinster, Ireland, the world justice, but with he and fellow veteran Cullen retiring at the end of the season, this clash could be there last.
Matt O'Connor's men, defending their title and finishing top of the league standings, will be determined to send the duo out on a high, adding the PRO12 crown to the Six Nations Championship won in Paris almost exactly two months ago.
The head coach keeps faith with Kiwi fly-half Jimmy Gopperth, who has battled Ian Madigan for the number ten jersey all season with both playing excellent rugby, and brings in Sean Cronin in the place of of Richardt Strauss at hooker.
It's a stellar lineup, but Ulster will not be daunted. Missing at least half of their first team, an inexperienced outfit took on the mighty Munster at Thomond Park last week and won well; the future is bright in Belfast.
Indeed, with all the talk over the so-called BOD Bash and farewell party, it is reasonable to assume Ulster are growing a little tired of the romanticism, especially when their own captain Muller is poised to hang up his boots when their involvement with the PRO12 comes to an end.
Iain Henderson said as much in a Belfast Telegraph interview this week, stating: "I wouldn't be too worried about sending those guys off on a low. I'd be a lot more interested in sending our captain Johann (Muller) off on a high.
"We want to win this competition so that means we have to win this weekend's match for there to be another one.
"And anybody who wants to go on the Ireland tour will have to put in a good performance.
"Each time you play you know the Ireland coaches are going to be watching so you have to make sure that in every game you're doing the best you can."
And indeed, the visitors will be massively buoyed by the respective returns of Ruan Pienaar and Rory Best from injury - presumably, the pair are not totally match fit, but their influence and the impact their mere presence in the Ulster lineup has cannot be understated.
They are joined by Kiwi Jared Payne who lines up opposite O'Driscoll at outside centre, with Craig Gilroy, Tommy Bowe and Andrew Trimble making up a lethal all-Irish back-three, and powerful flanker Robbie Diack returning to blindside.
Form: Leinster are playing in a fifth successive home Play-Off, whilst they have not finished outside the top three since season 2003/04.
The Leinstermen's solitary defeat in their last 12 RaboDirect PRO12 matches came on a visit to Ospreys in round 19.
Leinster were the only side to remain undefeated at home in the competition this season, their last PRO12 defeat at the RDS coming at the hands of Ulster on 30th March 2013.
Ulster have reached the Play-Offs in three of the last four seasons, but their only victory came last season at home to the Scarlets.
The Ulstermen have won just two of their last five PRO12 encounters and have beaten a fellow Irish province on their own soil in four of the last five regular season matches they have played.
Leinster have won their last three matches against Ulster including last year's final played at the RDS. They were also victorious over Ulster in the knock-out stage in 2011 at the RDS.
Ulster's only previous victory at the RDS in nine visits came in March 2013.
Prediction: Even with the returning Pienaar and Best, a win at the RDS will be a bridge too far for Ulster. Leinster by 5!
Leinster: 15 Rob Kearney, 14 Fergus McFadden, 13 Brian O'Driscoll, 12 Gordon D'Arcy, 11 Dave Kearney, 10 Jimmy Gopperth, 9 Eoin Reddan, 8 Jamie Heaslip (c), 7 Shane Jennings, 6 Rhys Ruddock, 5 Quinn Roux, 4 Devin Toner, 3 Martin Moore, 2 Sean Cronin, 1 Cian Healy
Replacements:16 Aaron Dundon, 17 Jack McGrath, 18 Mike Ross, 19 Leo Cullen, 20 Sean O'Brien, 21 Isaac Boss, 22 Ian Madigan, 23 Zane Kirchner
Ulster: 15 Craig Gilroy, 14 Tommy Bowe, 13 Jared Payne, 12 Darren Cave, 11 Andrew Trimble, 10 Paddy Jackson, 9 Ruan Pienaar, 8 Roger Wilson, 7 Chris Henry, 6 Robbie Diack, 5 Johann Muller (c), 4 Iain Henderson, 3 Ricky Lutton, 2 Rory Best, 1 Calum Black
Replacements: 16 Rob Herring, 17 Andrew Warwick, 18 Adam Macklin, 19 Dan Tuohy, 20 Sean Doyle, 21 Paul Marshall, 22 James McKinney, 23 Luke Marshall
Date: Saturday 17th May
Kick-off: 1900 BST
Referee: Leighton Hodges (Wal)
Assistant referees: Ian Davies (Wal), Neil Paterson (Sco)
TMO: Gareth Simmonds (Wal)