Coming just a week after their remarkable Heineken Cup final turn-around against Northampton, Leinster coach Joe Schmidt suggested fatigue played its part at Thomond Park but it was not the first time Horgan's side at fallen at the final hurdle.
Twelve months previous, Leinster were downed by the Ospreys on home turf at the RDS Arena - and Horgan is insistent there will be no third consecutive disappointment this time around.
"The loss to Munster does sting. It was the last competitive game we played," said Horgan. "The Heineken Cup was fantastic but the Munster game was obviously a big focus as well. We didn't go out to roll over against Munster ever, especially in a league final.
"We competed until the final whistle, but we seemed to be lacking a bit of an edge that day, we were hit by a couple of injuries but more than anything, Munster were extremely committed, extremely skilful and they performed better than we did and fully deserved their win.
"When you are beaten like that fair and square, it's tough as well and you have to reassess how we will compete with them next time.
"Those derbies become bigger and bigger every year so we are excited looking forward to those games.
"It's two finals in a row that we have lost and it's not acceptable from our point of view. It's horrible that you do all that work for a year and there's an amazing amount of work that goes in to get yourself into a position to get into the top four and then work through those really difficult weeks in April and May to try and get it into a final.
"And then to leave it out there is not great. There are two potential cups that we don't have and that does sting, and it's certainly not a hat-trick we fancy completing."
A troublesome knee problem hampered Horgan towards the end of last season and after it flared up in the defeat to Munster, any slim hopes he was harbouring of being included in Declan Kidney's World Cup squad were extinguished.
But even if fully fit, Horgan is the first to admit that having last played for Ireland in November 2009, it's unlikely he would have added to his 65 caps at a third World Cup in New Zealand - conceding club rugby is now his sole priority.
"The World Cup really wasn't on my radar," he added. "I think that stage of my career was over, there wasn't really any expectation and as it happened with the injury, that took the decision out of my hands.
"It's been two years now anyway so it's right that there's been a shift which has gone extremely well. My entire focus is on Leinster and that takes a lot of time and commitment."
63x46.png){kind=logo}