Leinster came through an incredible game to slip past Ulster 21-18 in the Champions Cup quarter-finals at the Aviva Stadium on Saturday night.

IT'S ALL OVER!

WHAT. A. GAME.#LEIvULS #JoinTheRoar pic.twitter.com/CJlds9IeDr

— Leinster Rugby (@leinsterrugby) March 30, 2019

The win now means that the home side will face Toulouse in the semi-finals and leaves the prospect of an all Irish final alive.

Ulster got off to a flying start as they put in a couple of crunching tackles on the hosts and were rewarded for their pressure in first five minutes.

Garry Ringrose took the decision to kick even with Ulstermen chasing him, leading Iain Henderson and Rory Best charging the kick down for Kieran Treadwell to pounce for an easy try.

Ulster strike first! ?

Kieran Treadwell pounces on a blocked kick…

And just listen to that ROAR! ?

Incredible start for the "away" side in Dublin… pic.twitter.com/40phLF2LO2

— Rugby on BT Sport (@btsportrugby) March 30, 2019

John Cooney slotted home the conversion and it was 7-0 with six minutes on the clock. A dream opening for the underdogs.

However, Leinster bounced-back almost immediately, going through the phases before Ross Byrne chose not to pass but to carry instead and in the tackle with an outstretched arm touched the ball down.

He missed the conversion to leave matters at 7-5 to the away side with only 11 minutes gone.

The high-intensity continued and Ulster captain Best went off after 16 minutes due to an ankle injury.

Byrne was handed a penalty opportunity in front of the posts 50 metres out midway through the half, only for him to send it wide once more.

Cooney had no such problems from the tee when given his chance from a Cian Healy penalty moments later, and instead of Leinster going ahead four minutes previous they were now 10-5 behind.

Just past the half-hour mark Byrne began to make up for his errors. Landing a penalty following a Nick Timoney infringement.

Another Byrne penalty soon after put Leinster in the lead for the first time.

Although it was the visitors who went in smiling at half-time with Cooney kicking his second penalty of the night to make it 13-11.

It's tight at the Aviva ?@leinsterrugby held a lead for a few minutes but it's @UlsterRugby with the advantage at the break…

Which way is this one going?? ? #Heineken #ChampionsCup pic.twitter.com/ESJNXBzu3F

— Heineken Champions Cup (@ChampionsCup) March 30, 2019

The incredible pace of the opening half continued when the sides returned, and Ulster should have stretched their lead five minutes in.

Jacob Stockdale flew down the wing following a pass on the blindside from Billy Burns, leaving Leinster men in his wake. He got to the try-line as Dave Kearney put in a routine tackle past the line as it looked like Stockdale had scored his seventh try of the tournament.

It wasn’t to be though, as replays showed that he had knocked the ball on while trying to place it one handed, and Leinster gasped a huge sigh of relief.

"This, unfortunately for Jacob Stockdale, is unforgivable!"

"He'd done all the hard work, all he had to do was fall!"@BrianODriscoll and @StephenFerris6 weigh in on the moment that shifted the momentum of the whole game…

A cruel, cruel blow for Ulster. pic.twitter.com/851lr4WwkM

— Rugby on BT Sport (@btsportrugby) March 30, 2019

Within minutes that mistake seemed crucial as the host pounded the opposition defence before man of the match Jack Conan decided to have a pick and go from the back of a ruck and sprint forward.

? @JackConan1 made a crucial break for @leinsterrugby today but he put in the groundwork everywhere else on the pitch too ⛽️

Will he be a key figure in the #Heineken #ChampionsCup semi-finals? pic.twitter.com/5eoazzcoWR

— Heineken Champions Cup (@ChampionsCup) March 30, 2019

He, much like Stockdale previously, left defenders looking at the back of him, all the while trying to pull up his shorts. He was eventually taken down by Stockdale only to deliver a beautiful offload to Adam Byrne, who finished off the move.

HUGE try for Leinster! ?

Sensational play from Jack Conan and Adam Byrne touches down in the corner!

The Ireland back-rower even managed to pull his shorts up mid-break, outstanding! ? pic.twitter.com/FCx85VJ9y0

— Rugby on BT Sport (@btsportrugby) March 30, 2019

Ross Byrne delivered the extras and it was 18-13 to Leinster.

A long delay followed minutes later as replacement Dan Leavy, who only returned to action last weekend, went down with what seemed to be a very serious knee injury.

During that time Ulster centre Luke Marshall, who himself was returning to action for the first time since last May came on and with only his second touch of the game scored a fine try to bring things level.

Heartbreak for @UlsterRugby who came very close ?

Small margins ? but they still managed some quality #ChampionsCup rugby as seen in this late try from @lukemarshall121 ✨

Were they the better side on the night? ?‍♂️ pic.twitter.com/OFXh1AIrjI

— Heineken Champions Cup (@ChampionsCup) March 31, 2019

Cooney stepped up and uncharacteristically missed the conversion as they went into the final stages at 18 all.

Ross Byrne went down with cramp on more than one occasion over the next few minutes, but when Leinster put the pressure on and earned a penalty, he took responsibility. Sending the kick through the posts to make it a three-point game with seven minutes remaining.

Ulster continued to search for a score, but it was Leinster who ended the game in the opposition 22, as they almost went over for a try, going through 44-phases before Luke McGrath kicked the ball out to confirm the 21-18 win.

LEINSTER HAVE DONE IT!

What a thrilling game, it ends 21-18 to the defending champions ?

The boys in blue are back in another Champions Cup semi! pic.twitter.com/rbiyHwXrom

— Rugby on BT Sport (@btsportrugby) March 30, 2019

After the game, Leinster head coach Leo Cullen admitted his relief at winning and knows his side will have to be better going forward.

“We are relieved to be through to the semi-final. I don’t think we were anywhere near our best. We know we are in two semi-finals, but it’s about how do we build cohesion and our levels of performance so that when it comes to those games, we give a better account of ourselves than we did today,” he said while speaking to RTE Sport.

The win means Leinster are in with a chance of retaining their European crown, but it may have come at a cost with Leavy’s injury and the possibility of losing Byrne to injury also. While Ulster will rue a missed opportunity to dethrone their rivals in what was an epic encounter.

Player Ratings:

Leinster: Jordan Larmour (6), Adam Byrne (7), Garry Ringrose (6), Rory O’Loughlin (5), Dave Kearney (7), Ross Byrne (8), Luke McGrath (7); Cian Healy (6), Sean Cronin (6), Tadhg Furlong (7), Scott Fardy (8), James Ryan (7), Rhys Ruddock (7), Sean O’Brien (6), Jack Conan (9)

Replacements (8)

Ulster: Michael Lowry (6), Rob Baloucoune (7), Darren Cave (7), Stuart McCloskey (7), Jacob Stockdale (7), Billy Burns (6), John Cooney (8); Eric O’Sullivan (6), Rory Best (6), Marty Moore (7), Iain Henderson (8), Kieran Treadwell (9), Nick Timoney (6), Jordi Murphy (7), Marcell Coetzee (7)

Replacements (8)

"I just wish I wasn't pulling at my shorts for about 20 meters!" ?

A typically humble Jack Conan sees the funny side of his outstanding effort for the game-deciding score…

Today's man of the match believes Ulster are the toughest test Leinster have faced all season ? pic.twitter.com/HnmrBz7Ofr

— Rugby on BT Sport (@btsportrugby) March 30, 2019

Match Highlights:

An instant #ChampionsCup classic at the Aviva Stadium ?@UlsterRugby and @leinsterrugby threw everything at each other in a thriller ?

Leinster go marching on in the competition winning 21-18 ✨ pic.twitter.com/nweC9x4eCX

— Heineken Champions Cup (@ChampionsCup) March 31, 2019