Christian Pulisic, Pierre-Emerick Aubameyang doubtful for Dortmund

Borussia Dortmund's injury woes continue ahead of their DFB Pokal match against German second-tier club Union Berlin.

United States international Christian Pulisic as well as attacker Pierre-Emerick Aubameyang and winger Ousmane Dembele are doubtful for the second round match at the Westfalenstadion.

Dortmund have played in and lost three consecutive cup finals, and go into their meeting with Union Berlin as the big favourites.

However, their injury crisis worsened following the dramatic 3-3 draw at Ingolstadt at the weekend.

"Christian Pulisic, Ousmane Dembele and Pierre-Emerick Aubameyang all did not train today," BVB coach Thomas Tuchel told his prematch news conference on Tuesday.

"That's bitter news for us. It's totally questionable whether they can be called up to the squad tomorrow. Two of them are ill, and Auba received several knocks against Ingolstadt."

At Ingolstadt, an experimental Dortmund side playing in an unusual 4-4-2 system struggled against the hosts, but came back from a 3-1 deficit with Pulisic, 18, scoring the last-minute equaliser.

Dortmund will also be without captain Marcel Schmelzer, Portugal international Raphael Guerreiro as well as Germany stars Andre Schurrle and Marco Reus, with the latter making steady but slow progress after returning to team training following a five-month injury layoff earlier this month.

"It will take weeks," Tuchel said when asked about Reus' return to the matchday squad.

Up to 12,000 Union Berlin fans will travel to Dortmund as they hope to upset the Bundesliga giants.

The club, trained by former Schalke coach Jens Keller, have enjoyed a good season so far and currently rank second in the second tier.

"We still feel capable of winning such a match," Tuchel said, adding that the new injuries made the situation even more "complex" and calling for his team to show "team spirit."

Union Berlin coach Keller, meanwhile, said that he is looking forward to playing a good team in great atmosphere at the Westfalenstadion, but added that the "on paper" the fixture "does not look like it will be played at eye-level."