A late Ian Madigan try broke Ulster hearts as Leinster overturned a 9-0 deficit to win 13-9 and reach the PRO12 final on Saturday.
The opportunistic try from the substitute, along with an accomplished kicking display from pivot Jimmy Gopperth, enabled Leinster to prevail in an absorbing, but flawed semi-final at a sun-soaked RDS.
A courageous Ulster were the better side for large portions of the match, but ultimately could not translate territorial dominance into points on the scoreboard.
The Ravenhill side, who led at half time, contributed three penalties from the boot of Paddy Jackson, but fell victim to a clinical and efficient second half comeback from their compatriots. The game ebbed and flowed, but a streetwise Leinster refused to be beaten, and just about deserve their place in the final. Brian O'Driscoll will thus have another opportunity for a swansong that may yet yield him another winners' medal.
The game, as expected, started with some thunderous collisions, and Ulster showed their intent by going through the phases in the first couple of minutes.
The de facto visitors started well, and earned themselves a penalty attempt on the three minute mark, but Pienaar could not convert the effort. Jackson succeeded in getting his side on the scoreboard with a six minute penalty; resulting from Gordon D'Arcy being caught offside following sustained Ulster pressure. The fly-half made no mistake with the straightforward kick to give his side a 0-3 lead.
Leinster struggled to win decent ball during this phase of the match, and seemed to have been somewhat surprised by the intensity displayed by the men in white. But the Blues eventually settled, and were galvanised by both their superb defensive organisation, and the tangible superiority of their scrum.
Therefore the league leaders gradually edged their way into the match, but despite starting to win their fair share of ball, created very little behind the scrum.
A rare exception was a dazzling run by Fergus McFadden on 23 minutes that cut the Ulster defence in two, but the Leinster back line just wasn't clinical enough to get over the whitewash; frustratingly conceding a penalty that allowed Ulster to clear their lines. In fact, the narrative for much of the first half was defined by the sterling work of the Ulster forwards, who were providing good, clean ball for Pienaar and his fellow backs.
But for all Ulster's endeavour, the pressure being exerted on their front row will certainly have caused them concern. To be honest, although gripping, the first half contest was a fairly uninspiring affair, with both sides struggling to attain any real rhythm in their play.
Despite Leinster improving vastly as the half progressed, Ulster were just about still on top as the game approached the interval. And it got even better for the Belfast side on the 40 minute mark when Jackson successfully slotted another penalty to make it 0-6, after Jack McGrath was pinged for offside. Given the prize at stake, it was the Ravenhill men, therefore, who would have been happier with their performance during the first period.
The second half commenced with the outcome still very much in the balance. Leinster's cause wasn't helped when the iconic O'Driscoll departed from the field in a dazed condition, having been involved in a collision with Iain Henderson.
Jackson augmented Ulster's lead on 52 minutes when he landed another penalty to make it 0-9. The fly-half seemed to injure himself in the process, though, and left the field minutes later.
Gopperth earned his side's first points on 58 minutes when he reduced the deficit to 3-9. Given the discernible lack of space, the Blues still had much to do, however.
But the momentum seemed to have switched inexorably in Leinster's favour at this stage, and Gopperth kicked another penalty on 63 minutes to narrow the gap to a mere three points. As the game entered the last 10 minutes, the winner was still anyone's guess.
And with the Blues putting Ulster under considerable pressure, Madigan sliced through a gap in the their defence on 72 minutes to touch down. Gopperth converted to give Leinster a two point lead.
The northern province laid siege to the Leinster line in the final minutes in a desperate attempt to regain their lead, but the Blues' defence was simply outstanding. Ulster battled right to the final whistle, but just couldn't penetrate a formidable Blues' rearguard.
It may not have been Leinster's most attractive display of the season, but you have to admire their tenacity and sheer will to win. In the final analysis, it was the Dublin side's big-game experience that ultimately made the difference in this match.
Heartbreak yet again for a spirited Ulster, but it is the familiar faces of Leinster who will join Glasgow in the PRO12 decider.
By Rory McGimpsey
Pens: Gopperth 2
Yellow card: D'Arcy
Pens: Jackson 3
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
Referee: Leighton Hodges (Wal)
Assistant referees: Ian Davies (Wal), Neil Paterson (Sco)
TMO: Gareth Simmonds (Wal)