Leinster head coach Leo Cullen rued his side's poor finishing but hoped they would learn a lesson after the reigning URC champions were shocked by rivals Munster in Croke Park.
Leinster entered this game with just one win from three, following a disappointing South African tour where they picked up just two points out of a possible ten.
However, despite having 12 Lions in their matchday squad, the 51,000 attendees in Croke Park were left stunned as Munster pulled off a major upset.
Like last season’s encounter, Leinster made a fast start, but this time around, it was the visitors who were more clinical with their opportunities.
"I thought we started the game okay", Cullen told RTÉ Sport.
"We scored a good try at the start. Munster come back into it, we don't exit effectively, and hence they're down our end. They do well from a close-range try and they get over.
"We were probably in that position 12 times in the game where we don't get over, because we're chasing the game."
Munster’s first-half tries from Brian Gleeson, Tom Farrell and Ethan Coughlan put them in the driving seat, but Leinster couldn’t claw their way back in the ‘championship minutes’, as they so often do.
For Cullen, this period was crucial.
"We had a chance before half-time to score, where Munster are scrapping and fighting for everything and you've got to give them a huge amount of credit for the way they went about things. They were able to hold us out before half-time," he said.
"We started the second half pretty well, I thought, and were in a good position. We have a lineout and we have lots of these pick-and-go opportunities close to the try-line.
"But Munster are just so effective and we're just lacking a bit of composure there. Is that because it's the first game of the season for a lot of guys or whatever that is? Or is it Munster are very good and we're just not quite accurate enough? There's a few different factors there at play."
On what was a frustrating night, Cullen looked to the bigger picture, ahead of a strange schedule where Leinster now lose their 21 Ireland players for five weeks.
"It's a good wake-up for the group," he said.
"We had a group that was out in South Africa, and we have a cohort of the Lions guys. It's always going to be a bit of a sticky start to the season for us. We've talked about it over the last while and now we're seeing it unfold.
"You talk about it and hope that that's not going to be the case, but you're marking everyone's card, our own in particular. We've still got to go through it and we weren't good enough today.
"But the big thing is composure, taking opportunities. Munster were a hell of a lot better than we were.
"We're just not battle-hardened at the moment. It is what it is. I'm not sure exactly what the solution is for us moving forward. How we get to that physical pitch and speed of playing games."
The result sees Leinster outside the top eight in the URC ahead of the final game of the ‘block’ next week against Zebre, which the focus is now on.
"The challenge for us in the short term is we have a cohort that are going to be gone next week and we're playing Zebra at the Aviva.
"I'd love to be coming into the press here talking about a big performance here and sending guys off into national camp, and talking about the group that we have getting ready to play against Zebre and the opportunity that's there for a number of players.
"We'll have a number of guys making their debut next week, but unfortunately, I'm talking about how we were sub-par today."
Munster, in the words of Cullen, outfought their arch-rivals, to which the Leinster stalwart admired.
"I heard Clayton talk about hard work, grit, determination. They showed that in spades, didn't they?" he said.
"Whereas we were second in hard work, grit and determination and we just need to take that on the chin and be better next time."
Leinster will face Zebre next week and then the Dragons late in November, after Ireland’s Autumn Nations Series campaign.
