Atalanta defeated Bayer Leverkusen 3-0 in May, ending the German champions' remarkable unbeaten streak, and will be up against European champions Real who beat Borussia Dortmund 2-0 to lift their record-extending 15th Champions League trophy.
"On paper, we're even more of an underdog than we were against Leverkusen, who were coming into the (final) game unbeaten in an entire season," Gasperini told a press conference on Tuesday.
"Real Madrid will be an even greater hurdle but that means we're even more motivated. It doesn't happen often but you can overturn the odds in football."
Atalanta will, however, face an extra challenge in Warsaw as they have travelled without injured striker Gianluca Scamacca.
The Italy forward, who scored six goals in their winning Europa League campaign, ruptured his anterior cruciate ligament (ACL) in a pre-season friendly defeat by Parma (4-1) on Aug. 4 and could be out of action for at least six months.
They will also be without Netherlands midfielder Teun Koopmeiners who Italian media reports said is nearing a move to rivals Juventus.
"It's clear that you'd like to go into such a game with a full squad and play your best players to get to the top of your game," Gasperini said.
"But even when we went to Liverpool or other (top) teams, and we often found ourselves with some difficulties, I always asked the guys to play a good game, without thinking of who's there or who's not there."
Winger Ademola Lookman said Atalanta should not be underestimated.
"We can't wait to get on the pitch. Not just me, but the whole team can't wait to play this match," Lookman said.
"We deserve to be here. Our hard work and perseverance have brought us here and tomorrow is another night to show that."
Lookman's hat-trick sealed the Europa League for Atalanta, their second major trophy after they won the Italian top flight in the 1962/63 season.
