Leinster have won all 15 games of a truncated PRO14 campaign and were also unbeaten in qualifying for the last eight of the Champions Cup.
Their last defeat came against Saracens, their opponents in the quarter-finals next month, in last season's Champions Cup final almost 16 months again.
However, Lancaster insists that all those results will count for nothing if they lose on Friday and has urged the squad not to lose focus.
"It’s absolutely irrelevant how many games we’ve won prior to this semi-final,” he said.
“I remember in the 2016/17 season we played some great rugby across the board, scored 90-odd tries in the season but we lost against Scarlets in the PRO14 semi-final and that defeat still sticks in everyone’s throats until this day.”
The former England head coach believes that the intense competition for places within the Leinster camp works well in preventing any complacency setting in and he hopes that remains the case ahead of Friday night's game.
"I think it’s the internal competition, if I’m being honest," he said. I wouldn’t say it’s the favourites thing, but if you’ve been through a series of games you’ve won, the easy thing to do is to think ‘Well, we’ll win the next game’. It’s not conscious complacency but it’s a subconscious mindset that can develop.“It’s very, very difficult for that to seep in here because you’ve always got very good players who are always striving to get into the team and the team is constantly being rotated and freshened up, so no-one sits there comfortably thinking, ‘I’ve got this in the bag’.
"That’s the real strength of Leinster’s competitiveness at the moment.”
***See BOTH PRO14 sem-finals LIVE this weekend on eir sport.