Union emerged 2-0 winners when the sides met last month, and sit 10 points clear of their hosts in the Bundesliga standings, but have never before claimed the German cup.
Match preview
With their momentum stalled since losing to Napoli in the first leg of their Champions League last-16 tie, Eintracht Frankfurt have since been beaten by RB Leipzig, then the Serie A leaders again, and then this week's cup opponents Union Berlin.
During that spell, Die Adler have not won once, drawing all of their other fixtures in the Bundesliga to slip behind in the top-four race - they now trail fourth-placed Freiburg by six points.
Two more points were dropped by Oliver Glasner's men on Friday, as a 1-1 draw with Bochum - which saw top scorer Randal Kolo Muani find the target again - made it five league games without a win.
They therefore return to action at Deutsche Bank Park with a previously promising campaign threatening to peter out, so finding a way past in-form Union would both boost confidence in the camp and keep dreams of more silverware alive for last year's Europa League winners.
Despite Kolo Muani being sent off when the teams last met in Frankfurt, back in October, the hosts secured a 2-0 victory over their capital-city counterparts on that occasion, but the dynamic between the pair has certainly changed since then.
Their star man struck twice in the previous round of the DFB-Pokal, when Eintracht dumped Darmstadt out by winning 4-2 in their last-16 tie, and Glasner will now turn to the France international for inspiration once again.
While they were also eliminated from continental competition before the international break, in contrast to Frankfurt, Union Berlin have kept their pursuit of a Champions League place on track by staying on the coat-tails of Germany's top two.
Sheraldo Becker's second-half goal on Saturday ended an 11-game drought for the Suriname striker and set Die Eisernen towards a 3-0 victory over struggling Stuttgart; consolidating third place in the standings.
With 51 points after 26 matches, Union are enjoying their best-ever Bundesliga season so far, and they are now only two points adrift of Borussia Dortmund, who imploded in Saturday's top-of-the-table Klassiker contest against Bayern Munich.
As a result of their latest success at Alte Forsterei, Urs Fischer's side are the only team other than Bayern still unbeaten at home in the league, but they have been less impressive on the road and were beaten 3-0 away to Belgium's Union Saint-Gilloise in their recent Europa League tie.
Nonetheless, Berlin's rising stars knocked out Wolfsburg to reach the DFB-Pokal's last eight and will be intent on breaking more new ground by going all the way in this season's competition.
Despite once lifting the East German Cup in the 1960s, the closest they have come to claiming cup glory since reunification came back in 2001, when they lost the final to Schalke as a third-tier team - it has been a long road to prominence since then.
Eintracht Frankfurt DFB-Pokal form:
W
W
W
Eintracht Frankfurt form (all competitions):
L
D
D
L
L
D
Union Berlin DFB-Pokal form:
W
W
W
Union Berlin form (all competitions):
D
D
D
L
W
W
Team News
In addition to Hrvoje Smolcic, who will miss the rest of the season, Oliver Glasner will once again be without in-demand winger Jesper Lindstrom (ankle) and Malian defender Almamy Toure (thigh) due to injury on Tuesday.
Centre-back Tuta returns after a one-match ban and could slot into Frankfurt's back three, but there may not be many more changes to the starting XI that lined up against Bochum.
Union Berlin, meanwhile, will remain without Andras Schafer, who is still sidelined by a foot problem, while first-choice goalkeeper Frederik Ronnow was a last-minute withdrawal from the team that saw off Stuttgart.
Stand-in stopper Lennart Grill would therefore be called upon again if Urs Fischer is again deprived of his regular number one.
Up front, Sheraldo Becker is Union's eight-goal top scorer in the Bundesliga this season and he could be partnered by Kevin Behrens - the club's leading marksman in 2023 and a scorer in the win over Wolfsburg in the DFB-Pokal's last 16.
Eintracht Frankfurt possible starting lineup:
Trapp; Tuta, Hasebe, Ndicka; Knauff, Rode, Sow, Max; Kamada, Gotze; Kolo Muani
Union Berlin possible starting lineup:
Grill; Doekhi, Knoche, Leite; Juranovic, Laidouni, Khedira, Haberer, Giesselmann; Becker, Behrens