Head coach Leo Cullen admits Leinster were pushed to the limit by Ulster

Chasing the underdogs for most of the game the defending champions once again showed their experience of having played - and won - seven of their eight previous quarter-finals.

The 21-18 margin reflected how hard Ulster had pushed the men in blue in a sell-out Aviva Stadium.

“We were definitely worried Ulster would come here with the game of their lives,” admitted Cullen.

“You are always so wary about teams that are close and are building and building.

“They have a lot of positive momentum there and they’ve had disappointing days.

“We talked about all the threats that they have,” said Cullen. “(Stuart) McCloskey in the middle of the field gives them go-forward, good direction.

“And everyone is talking about Leinster are going to win and it’s just a matter of turning up.

“That’s just not the way it actually works in reality.

“Then, you have a slow start in the game on top of that and you have to chase the game. It is always difficult.

“Any game when you are chasing it is tough going in Europe with the quality of teams that are there.

“Ulster have had to fight through a number of really tight games this year.

“That makes them very dangerous because they’ve been in that situation and the know what to do, how to manage the game.

“We’re through to the next round. But, - and it’s a big but - we’re pretty fortunate as well.”

Ross Byrne completed his 16-point haul for Leinster with a decisive penalty, nine minutes from the end which sealed the victory and kept the Irish Province en route to a potential record fifth Cup success in Europe - and they already have secured their semi-final spot in the Guinness PRO14.

Cullen said: “We know we’re in two semi-finals now (in the Guinness PRO14 and Champions Cup), but it’s about how we build the cohesion and our levels of performance so that, when it comes to the two semi-finals, we give probably a better account of ourselves than we did today.

“We’re always having to chase the game from so early.

“Once Ulster had the lead, they were able to play that pressure game on us.

“We didn’t respond particularly well to it, I didn’t think.

“But ultimately we got the job done. It’s pleasing on one hand, but frustrating on the other.”