Leinster were made to sweat before s queaking into another European semi-final rugby by defeating Ulster at the Aviva Stadium on Saturday.
Ulster can be proud of the way they played, right up to the final whistle, and had Irish and Ulster winger Jacob Stockdale not been so complacent in putting the ball down when he was five metres over the try-line, this result could have signalled one of Ulster's greatest ever victories.
Stockdale won't make the same mistake again. The Ulster winger, despite having an excellent day in general play, will feel that he let his team-mates down.
Ulster struck first when centre Garry Ringrose had his exit kick blocked down for the visitors to draw first blood. But instead of consolidating, Ulster let Leinster straight back into the game, and that was the story of the day.
Leinster just had too much experience and composure when it mattered most. They have that ability to hit back immediately so that the damage doesn't become permanent.
Ulster's line-speed, aggression and ball-carrying were causing Leinster all sorts of problems early on. Leinster's own carriers were swallowed up, although they did look dangerous when the ball made it into the outside channels, where Adam Byrne, Jordan Larmour and Ringrose all looked as if they could create some magic.
Games this tight are always about small margins and when Ulster had a chance to put a little breathing space between the teams, Stockdale fluffed his lines.
The Ulster winger is a prodigious talent and it was his individual brilliance that created the opportunity in the first place. But he failed to remember the basic rule of scoring a try - get to ground early with the ball safety tucked under your arm, or at the very least with both hands on the pill.
Instead Stockdale, well into the scoring zone tried to put the ball down with one hand and lost control.
Leinster then forced a scrum penalty and it allowed them to move out of danger and the momentum changed, although Ulster would score another try through replacement centre Luke Marshall.
The game's best score came after a rampant Jack Conan, one of Leinster's outstanding contributors on the day, found a huge hole behind Ulster's ruck. The big No 8 even had enough time to hitch up his falling shorts before getting the ball to the fast-tracking Adam Byrne who expertly finished.
Leinster exposed where Ulster were weakest, around the rucks, where the visitors' pillar defence was often absent. Leinster looked most dangerous when they didn't panic, and built the phases, as they did to wind down the clock in the final moments.
There were heroic performances on both sides. Ulster's Stockdale, Iain Henderson, John Cooney, Darren Cave and Stuart McCloskey were all excellent.
For Leinster, up front no players worked harder than Conan, captain Rhys Ruddock and second row James Ryan. Ross Byrne's kick to win the game was something out of the Boys Own annual.
Byrne, who played well in Johnny Sexton's absence, scored a good try in the first half. Struggling with cramp or a leg strain, you could see he had serious doubts about taking the winning kick but on one leg the young Leinster out-half struck the ball sweetly between the posts for the winning score.
Minutes later, he limped from the field. It showed the value of mind over matter. If Leinster go on to win the cup again, it may well be that very moment that saved their blushes.
Leinster will know that they will need to play a lot better than this to deliver another star on their chests. They will have to win without the services of Dan Leavy whose World Cup dreams could also be in doubt after being stretched off with a serious knee injury.