The visitors can move one point behind their forthcoming opponents with a victory.
Match preview
Union Berlin's upwards trajectory continues to know no bounds, with Urs Fischer's side staying at the top of the Bundesliga with a 1-0 win against Stuttgart last weekend.
Moreover, Die Eisernen ensured that they will compete in European competition after winter for the first time in their history by beating Malmo 1-0 on Thursday evening, courtesy of Robin Knoche's 89th-minute penalty.
Trailing second-placed Braga by one point in Group D of the Europa League, their meeting at Stadion An der Alten Forsterei in less than two weeks time is likely to be crucial in terms of determining which team progresses into the knockout stages or falls into the Europa Conference League.
In the meantime, though, Union have three domestic games to focus on, starting with a tough test against Dortmund in what is being billed as 'Super Sunday,' given that Freiburg and Bayern Munich also face each other later in the day.
Having beaten RB Leipzig and held Bayern at home already this season, Fischer's side have no reason to fear their forthcoming opponents, especially having beaten them in two of their three meetings on home soil since being promoted in 2019.
Dortmund, meanwhile, have shown decent resolve in the past week by coming from behind to claim draws against Bayern and Sevilla.
Dortmund fell two goals behind in Der Klassiker at Westfalenstadion last weekend, with Leon Goretzka and Leroy Sane striking either side of half-time, but Youssoufa Moukoko breathed life into the hosts 16 minutes from time before Anthony Modeste truly announced himself to the BVB faithful by equalising in the fifth minute of injury-time.
The comeback ensured that Edin Terzic's side remain level on points with their potential title rivals heading into Sunday's pivotal fixtures, although they will not want to lose any further ground on their forthcoming opponents even at this early stage of the season.
In the Champions League, Dortmund should only require one more point to progress to the knockout stages, after Jude Bellingham joined Kylian Mbappe and his former teammate Erling Haaland as the only teenagers to score in four successive Champions League matches to claim a point for his side.
Terzic will not want to see his side fall behind for a third consecutive match away to Union Berlin, whose defensive solidity generally makes them very difficult to peg back, as is evident by them winning three of their last four league games to nil.
Union Berlin Bundesliga form:
W
D
W
W
L
W
Union Berlin form (all competitions):
L
W
L
W
W
W
Borussia Dortmund Bundesliga form:
W
W
L
W
L
D
Borussia Dortmund form (all competitions):
L
W
L
W
D
D
Team News
Union Berlin's only absence is likely to be Kevin Mohwald, who is still recovering from a knock and unlikely to be risked.
As such, Fischer should be able to name what he feels is his strongest starting XI, with the in-form Jordan Siebatcheu and Sheraldo Becker combining in attack. The duo have directly contributed to 14 of their side's 16 league goals so far this season.
Dortmund, meanwhile, could welcome club captain Marco Reus back to their travelling squad, but the 33-year-old is extremely unlikely to start despite making an incredibly quick recovery from his ankle injury sustained in the Revierderby last month.
Jamie Bynoe-Gittens, Mahmoud Dahoud, Sebastien Haller and Mateu Morey remain sidelined, with Terzic's biggest dilemma perhaps being whether to start Moukoko or Modeste in attack after both strikers scored in Der Klassiker last weekend.
The former could win that particular duel due to his ability to drop deep and combine with the likes of Karem Adeyemi and Donyell Malen.
Nico Schlotterbeck and Raphael Guerreiro were held back until the second half against Sevilla in midweek, so should come back into the defensive unit fresh and raring to go against their opponent's fearsome front two, but Thomas Meunier is out after suffering a groin injury against the Spanish side and will likely be replaced by Marius Wolf.
Union Berlin possible starting lineup:
Ronnow; Jaeckel, Knoche, Leite; Ryerson, Schafer, Khedira, Haberer, Giesselmann; Becker, Siebatcheu
Borussia Dortmund possible starting lineup:
Kobel; Wolf, Hummels, Schlotterbeck, Guerreiro; Bellingham, Ozcan; Adeyemi, Brandt, Malen; Moukoko
We say: Union Berlin 1-1 Borussia Dortmund
Union Berlin are an extremely tough nut to crack, especially at Stadion An der Alten Forsterei, but we believe Dortmund have the confidence and attacking ability to return from the capital with a positive result.
Terzic's side should have gained serious belief from last weekend's comeback in Der Klassiker, and ultimately both teams may be content with a share of the spoils to consolidate their positions in the table.