And even though Clermont head into the historic encounter on the back of a hugely impressive quarter-final win at Saracens, Parra says everyone has been acutely aware of the size of the occasion during a tense week's training.
"It's been a weird week," said Parra, who has told his team-mates they must enjoy the pressure rather than be burdened by it.
"At the beginning of the week there was a lot of excitement, but during training we made some unusual mistakes.
"On Wednesday we had a contact session which we usually love but this time it was like everybody was scared. It was catastrophic. It looked awful.
"Leinster usually always perform well in these kind of big fixtures. They are used to it, but for us it is all new.
"We must really focus at the beginning on the game in particular because Leinster are very dangerous during the opening stages. And then we must stay calm. It's vital that we don't do stupid things just because of the excitement."
Clermont head to Bordeaux with two objectives in mind: the first is to reach the Twickenham showpiece on May 19 and the second is to establish themselves as a regular force in European rugby.
Parra insists he and his colleagues are better equipped than ever before for those dual targets and he admits he is relishing the chance to compete with the continent's elite in a tournament played at a tempo only international Tests can match.
"ASM Clermont want to be a big European club, to be a part of Heineken Cup history," added Parra.
"In European competition everything is going faster and the refereeing is different. It's a higher level.
"Everything has been done to succeed and every year we are evolving. We can't have any excuses. We can't say that we are not prepared or that we are not in good condition. The only excuse we have is if we are beaten by a better side than us. Leinster are the best European team but I know we can challenge them.
"This game is huge. So many players would love to be on the pitch on Sunday so we must perform at 100 per cent. It will be my first Heineken Cup semi-final and it could be my last. There is nothing more beautiful than that for a rugby player.
"For these huge fixtures you want to give even more than your best. It's so easy to find the motivation. One thing is for sure now - we must avoid questioning ourselves."