Wayne Pivac believes the Scarlets will need to overcome European rugby's "form horse" on Saturday when they target a place in the Champions Cup final.
The Welsh region contest a first European semi-final since 2007 by facing Leinster in Dublin.
Leinster, despite being drawn in a group that also featured Exeter, Montpellier and Glasgow, won all six games and collected 27 points from a possible 30 before knocking out European champions Saracens at the quarter-final stage.
And while the Scarlets will travel in confident mood, head coach Pivac knows how big the task lies ahead.
"They (Leinster) are unbeaten in the competition, and to do that home and away against the quality of their pool shows the strength of their squad," Pivac told reporters in Llanelli on Tuesday.
"It'll be nice to have the opportunity to go a step further in this competition, and we certainly know it's going to be a massive task.
"Leinster are the form horse, and we are going to have to have probably our best performance so far as a group.
"It is just going to be one of those games where, from the first whistle to the last, we've got to be at our best.
"Our discipline has got to be right up there. You give them the ball, and you don't see it for a while. They are very good at looking after possession, they have a strong set-piece and quality players across the field.
"It is a great challenge, and it's one where we aspire to be, playing against the best sides at this latter stage of the competition."
The Scarlets - last season's PRO12 champions - recovered from a poor start in Europe to end their pool fixtures by beating Bath and Toulon, then saw off quarter-final opponents La Rochelle.
All three of the Scarlets' previous European semi-finals ended in defeat, yet they have shown under Pivac that big games do not faze them.
After knocking out PRO12 semi-final opponents Leinster at Dublin's RDS last May, they returned to the Irish capital a week later and destroyed Aviva Stadium opponents Munster.
Pivac added: "We can certainly take a lot of confidence out of the fact we went to Ireland two weeks in a row, with one of those games at the Aviva.
"But it was 12 months ago. They are a different side, we are a different side.
"It is something we have worked towards for the last four years. It is very exciting times for the players, the club and the community in general.
"Hopefully, we can put up a very good performance that will reflect the hard work that has gone into getting us in the position we are in."