Meanwhile, their unfancied hosts have already competed against three different opponents in their pre-season period, claiming two wins and a draw in that positive sequence.
Match preview
Amid all the exhilarating contests that Leverkusen fought both continentally and domestically in the 2023-24 season, keeping hold of revered head coach Xabi Alonso - one of the most in-demand managers on the market - would seemingly be their toughest battle.
However, the Liverpool, Barcelona, Bayern Munich and Real Madrid-linked boss ultimately decided to snub a host of his former clubs and continue his work at the BayArena, after masterminding one of the greatest Bundesliga title triumphs in modern memory.
As if ending Bayern Munich's perpetual reign of Bundesliga supremacy was not enough of a magnificent feat in itself, Leverkusen did so without suffering a single defeat, winning 28 of their 34 matches; no other team in the history of the competition had ever earned an 'Invincibles' tag before.
Thanks to their magical run to the Europa League final - where heroic last-minute goals were commonplace - Leverkusen's unrivalled unbeaten run in all tournaments reached an astounding 51 matches, the longest European streak without defeat since UEFA competitions were introduced in the 1950s.
Alonso's men were not completely indestructible, though, as their historic unbeaten run ended at the hands of an Ademola Lookman-inspired Atalanta BC in the Europa League final, but Granit Xhaka did what Granit Xhaka does three days later, as his thunderbolt secured a Bundesliga and DFB-Pokal double for Alonso's captivating charges.
Sixty-nine years before Leverkusen ruled the land, upcoming hosts Rot-Weiss Essen were the team to beat in German football, winning their first and only top-flight crown to date in the 1955 campaign but only achieving far more modest results since.
Under the wing of Christoph Dabrowski - a 1998 Olympian with the German national team - since 2022, RWE have been slowly rebuilding since their insolvency crisis of 2010, finishing in a respectable seventh place in the 3. Liga last term.
A fourth-tier side as recently as the 2021-22 season, Rot-Weiss Essen were bottom-half battlers in their first season back in the 3. Liga in 2022-23, finishing 15th before shooting up the rankings last season and coming close to promotion playoffs qualification.
Dabrowski's men wound up just four points shy of the top three and have laid down some pre-season markers too, thumping local sides SGS Essen and Schwarz-Weiss Essen 5-0 and 4-1 respectively before going goalless against Hoffenheim II on July 14.
RWE now finalise their pre-season preparations on Friday, and it may come as a shock to learn that they possess fond memories of their last engagement with Leverkusen, whom they beat 2-1 in extra time in the last 16 of the 2020-21 DFB-Pokal.
Rot-Weiss Essen friendly form:
Team News
Despite widespread interest in some of their title-winning heroes - such as Florian Wirtz, Jeremie Frimpong, Edmond Tapsoba and Piero Hincapie - Leverkusen have not been forced into a major sale yet this summer, and there are rumours flying around that Jonathan Tah's proposed move to Bayern Munich could be about to collapse.
Tah and Wirtz are among the players still on a break following Euro 2024 and the Copa America, a list that also includes Robert Andrich, Xhaka, champion Alejandro Grimaldo, Frimpong, Hincapie and champion Exequiel Palacios.
Adam Hlozek, Patrik Schick and Matej Kovar might be involved sooner thanks to the Czech Republic's early Euros exit, though, while new signings Aleix Garcia, Martin Terrier and Jeanuel Belocian are in line for their unofficial debuts.
As far as RWE are concerned, Dabrowski is unsurprisingly unaffected by the summer international tournaments, but striker Moussa Doumbouya (groin) and midfielder Tom Moustier (foot) are both in the treatment room.
A name partially familiar to Arsenal fans, former Gunners academy product Thomas Eisfeld should be among the starters in midfield for Essen, while Jakob Golz - who was on the bench for the 2021 DFB-Pokal win over Leverkusen - is in line to start in goal.
Rot-Weiss Essen possible starting lineup:
Golz; Voufack, Schultz, Kraulich, Brumme; Kaparos, Eisfeld; Berisha, Kaiser, Safi; Vonic
Bayer Leverkusen possible starting lineup:
Hradecky; Tapsoba, Kossounou, Belocian; Tella, Garcia, Puerta, Adli; Hofmann, Terrier; Boniface
We say: Rot-Weiss Essen 0-3 Bayer Leverkusen
Even though Leverkusen are weakened by their players' recent Euros/Copa America progressions, Alonso's squad depth is enviable, and the Bundesliga champions should immediately pick up where they left off.