The Germany international - plagued by ankle problems in 2014 - was forced off midway through the first half of the third-round clash after colliding with Dennis Erdmann.
While it sparked fears over Reus potentially facing another lengthy lay-off, Jurgen Klopp initially explained Reus' injury was "only a dead leg".
"After further examinations on Wednesday, Dortmund confirmed Reus is merely a doubt for Saturday's Bundesliga clash with Hamburg and does not face weeks or months out of action," read a Dortmund statement.
"The first diagnosis of team physician Dr. Markus Braun has fortunately confirmed Marco Reus only suffered a painful bruise above the knee in the game with Dynamo Dresden.
"There is no danger of a longer-term absence. The 25-year-old international will be intensively supported by the medical department.
"Attention is being paid to how the bruise in the thigh muscle develops."
Reus has netted 11 goals this season and had scored in five consecutive matches prior to Tuesday's fixture.
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