Lukas Kwasniok's men are already the first club from the fourth tier to have ever made it this far in the competition, and they are now looking for a third Bundesliga scalp from their remarkable run.
When Saarbrucken beat Fortuna Dusseldorf in the DFB-Pokal quarter-finals in March, their vice-president Dieter Ferner described the achievement as "the biggest sensation since the birth of Christ".
Ferner would not have expected to wait more than three months for what came next, but success over Leverkusen would eclipse anything that has gone before.
No fourth-tier club has ever made it this far in the competition before - yet alone gone all the way to the final - and Saarbrucken are no stranger to the odds being against them.
That is most certainly the case for this match; the hosts will no doubt take confidence from the fact that they have already beaten Bundesliga sides Koln and Fortuna Dusseldorf during their dream cup run, but those two sides sit 12th and 16th respectively - Leverkusen are fifth.
Even aside from the quality of Leverkusen as a team, Saarbrucken will have to negotiate the unique challenge of not having played a competitive match of any note since March 7 - more than three months ago.
The Regionalliga campaign was cancelled as a result of the coronavirus pandemic, which was good news for Saarbrucken in that they were promoted and crowned champions having been top of the table at the time of lockdown, but bad news when it comes to match sharpness for this contest.
Leverkusen, by contrast, have played five times since the Bundesliga started up again, winning three and losing two - most recently a 4-2 defeat at home to top-of-the-table Bayern Munich.
Champions League qualification via a top-four spot, which they are currently only missing out on due to goal difference, is no doubt their priority for the remainder of the campaign, but success in the cup will be an alluring prize too.
Leverkusen have only ever won the DFB-Pokal once - in 1993 - and have not reached the final since 2008-09.
It would take one of the biggest shocks in German football history for them to be denied a chance to face either Bayern Munich or Eintracht Frankfurt in the final this time around, but Saarbrucken's journey has already been littered with magical moments.
The minnows have scored two injury-time winners in 3-2 wins and won two penalty shootouts, the last of which saw goalkeeper Daniel Batz make history with four saves to add to one from normal time, en route to knocking out two top-tier and two second-tier sides so far.
Before this season Saarbrucken had only played one DFB-Pokal match since 2013 and they needed to win last season's Saarland Cup to even qualify for this year's tournament.
The Leverkusen clash will be manager Kwasniok's sixth at the helm after he took over in December, but he could already be just 180 minutes away from leading the club to their first ever major trophy.
A European spot then awaits should they achieve that - not entirely uncharted territory for a club that took part in the inaugural European Cup in 1955-56 - but first they must surmount the sizeable hurdle of Leverkusen.
History, as well as present day, appears to be against them given that they have lost all three of their previous appearances in the semi-final of this competition, with their conquerors going on to lift the trophy each time.
Saarbrucken DFB-Pokal form: WWWW
Saarbrucken form (all competitions): WDWWWL
Bayer Leverkusen DFB-Pokal form: WWWW
Bayer Leverkusen form (all competitions): WWWLWL
Leverkusen's hopes of halting Bayern's title charge at the weekend were hampered by the absence of in-demand star man Kai Havertz, who failed a late fitness test.
The Bundesliga outfit are hopeful that he will be available for this match, although they will not take any unnecessary risks over his fitness.
Florian Wirtz will be hoping for a chance from the start, having become the youngest Bundesliga goalscorer of all time with his weekend strike against Bayern.
Saarbrucken's time off means that they have a fully-fit squad to choose from, including the competition's leading assist-maker Kianz Froese.
Saarbrucken possible starting lineup:
Batz; Barylla, Schorch, Uaferro, Muller; Janicke, Perdedaj, Zeitz, Mendler; Jurcher, Zellner
Leverkusen possible starting lineup:
Hradecky; Tah, S Bender, Tapsoba; Weiser, Aranguiz, Demirbay, Wendell; Bellarabi, Volland, Wirtz
We say: Saarbrucken 0-3 Leverkusen
Every neutral in the country will be willing another memorable upset, but this contest could be a step too far for the underdogs.
Saarbrucken's lack of match practice and the lack of home fans only adds to the unlikelihood of them pulling off one of the all-time biggest shocks in German football, so we are backing Leverkusen to safely progress into the final.