European Champions Cup: Leinster 21-18 Ulster
|European Champions Cup|
|Leinster (11) 21|
|Try: R Byrne, A Byrne Con: R Byrne Pens: R Byrne (3)|
|Ulster (13) 18|
|Try: Treadwell, Marshall Con: Cooney Pens: Cooney (2)|
Leinster's pursuit of a fifth European title remains on track but only after they had to dig deep to see off a spirited Ulster at the Aviva Stadium.
Tries by Ross Byrne and Adam Byrne helped the defending champions to come from behind and snatch a 21-18 win.
Kieran Treadwell's early try gave Ulster the lead but a missed chance for Jacob Stockdale proved costly.
Luke Marshall's try drew the visitors level but Ross Byrne's late penalty was enough to give Leinster the win.
The reigning champions will now face Racing 92 or Toulouse in their semi-final in three weeks' time.
Ulster will have to count the cost of a demoralising defeat that also saw Ireland captain Rory Best suffer an ankle injury on what could prove to be the final club appearance of his career.
- Relive Leinster's gripping win over Ulster
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Byrne shows his mettle
The absence of World Rugby player of the year Johnny Sexton from the Leinster starting team was met with apprehension by their supporters but Ross Byrne proved a capable deputy in the biggest match of his Leinster career.
The fly-half had to overcome a nervy start too - a loose pass to Garry Ringrose led to the centre's kick being blocked down and Treadwell diving over for the opening score with just six minutes on the clock.
But Byrne showed his class with a superbly-taken try just minutes later - bashing through Robert Baloucoune to score after the Leinster pack had battered at the Ulster line.
The Leinster kicker missed a long-range penalty but recovered well to convert a further two kicks and keep pace with counterpart John Cooney, who uncharacteristically missed a straightforward conversion that would have seen Ulster move back in front.
It was Byrne's final kick at goal that proved to be the match winner as he slotted a tricky shot through the posts despite clearly being hampered by cramp and he hobbled off to acclaim just moments later.
Ulster pushed for another score in the dying seconds but Leinster were able to finish the game in the opposition half and kicked the ball dead barely five seconds into injury time to clinch a thrilling win.
Ulster heroic in defence
Ulster came to Dublin knowing that they would have to produce their best defensive display of the season if they were to stop a Leinster side that were the top points and try scorers during the pool stages.
A ferocious tackle by Stuart McCloskey on Cian Healy set the early tone as the visitors thundered into every challenge and the home side repeatedly knocked on behind the gainline.
Best was a casualty of the gruelling start and the Ulster and Ireland captain was clearly emotional as he hobbled off with an ankle injury after 16 minutes.
The 36-year-old reappeared at full-time wearing a protective boot and using crutches and he now faces a fitness race to play for his home province before the end of the season.
Despite the absence of their leader, Ulster never looked out of their depth in the cauldron-like atmosphere that bubbled and hissed inside the Aviva Stadium.
Cooney punished any Leinster indiscipline, Michael Lowry was called back when he thought he had scored and the underdogs were full value for their 13-11 half-time lead.
A tale of two tries
From the restart, Ulster missed two glorious chances to press home their advantage.
Ringrose was again too casual with a clearing kick and was blocked down by Rob Herring but Billy Burns could not get to the ball as it bounced out of play.
The visitors missed an even better chance just moments later when Stockdale drifted past Adam Byrne, Jordan Larmour and Cronin but the normally lethal Ireland wing dropped the ball under pressure as he attempted a one-handed touchdown.
Leinster were not as wasteful when chances fell their way and they took the lead in the 54th minute with a superbly-taken try.
Number eight Jack Conan spotted a weakness in the Ulster defence and burst past Eric O'Sullivan and into open country before drawing the covering Lowry and sending Adam Byrne over for a fine score.
In an end-to-end contest, Ulster came back again and flung themselves at the Leinster line.
The pressure told with 15 minutes remaining when McCloskey's deep pass gave Burns time to pick out Marshall and the centre backed himself to steamroll through Ross Byrne on the line and mark his first appearance of the season with a score.
Crucially, Cooney missed the chance to nudge his side back ahead with the conversion and that mistake was punished when Leinster's maul won a penalty in the 71st minute that Ross Byrne somehow managed to convert.
Leinster 'a long way off' their best - Cullen
Leinster head coach Leo Cullen on BT Sport
"It was an amazing occasion, We are very thankful but in terms of performance we are a long way off our best.
"Integrating players back in, we looked like a team that have not played together in a long time. We were pretty disappointed by the way we went.
"We were edgy from the start. We were charged down in the first few minutes, we rode our luck at times and feel fortunate to advance to the semi-finals."
Leinster: J Larmour; A Byrne, G Ringrose, R O'Loughlin, D Kearney; R Byrne, L McGrath; C Healy, S Cronin, T Furlong; S Fardy, J Ryan; R Ruddock (capt), S O'Brien, J Conan.
Replacements: J Tracy for Cronin (58), E Byrne for Healy (58), A Porter for Furlong (67), M Kearney for Leavy (63), D Leavy for O'Brien (52), J Gibson-Park for McGrath (58), L McGrath for Gibson Park (HIA 65), N Reid for O'Loughlin (40), R Kearney for R Byrne (73)
Ulster: M Lowry; R Baloucoune, D Cave, S McCloskey, J Stockdale; B Burns, J Cooney; E O'Sullivan, R Best (capt), M Moore; I Henderson, K Treadwell; N Timoney, J Murphy, M Coetzee.
Replacements: R Herring for Best (16), A Warwick for O'Sullivan (73), W Herbst for Moore (56), S Reidy for Coetzee (52), L Marshall for Cave (63), A Kernohan.
Referee: Romain Poite (France)