Depleted Dortmund's depth to be tested once again vs. Union Berlin

Wednesday night Borussia Dortmund host 2. Bundesliga side Union Berlin in the second round of the DFB Pokal. Although the German cup is the most realistic chance for the Black and Yellows to win a trophy this season, the focus going into the match will be somewhat diverted to Saturday's big Revierderby against Schalke.

On paper, a home match against any side from Germany's second division should be a routine win. However, the most recent 3-3 draw against Ingolstadt gave proof that routine is exactly what Dortmund currently lack.

The Ruhr Side could only win one of their last five matches across competitions. Against Ingolstadt, they anticipated to turn their league form around after two winless matches.

"We were banking on claiming all three points," veteran goalkeeper Roman Weidenfeller said after Saturday's unexpected drop of points against inferior opposition. Yet, if it wasn't for a stoppage time equaliser by United States international Christian Pulisic, the Black and Yellows would have lost in embarrassing fashion.

"We were not ready to play in the Bundesliga," the Thomas Tuchel said about his team's frighteningly weak first half that saw them concede twice from nearly identical dead ball situations. "Not on a technical or tactical level, nor in terms of intensity and body language."

In the second half BVB showed spirit to battle their way back into the match, but easily could have conceded two or three more goals as well, after committing a couple of calamitous errors. One such error came from young Ousmane Dembele, who gave away the ball cheaply seconds after Dortmund pulled one back. Moments later Ingolstadt made it 3-1 to restore their two goal advantage.

The match at Ingolstadt perfectly epitomised the ups and downs in the Ruhr side's recent performances. Due to an ongoing barrage of injuries, Dortmund fielded their second youngest line-up in club history against Hertha Berlin, as having to make do without 10 outfield players, Tuchel's options were fairly limited.

Hence a lot of responsibility has been put on the shoulders of BVB's young players, such as 18-year-olds Pulisic and Felix Passlack and 19-year-old Ousmane Dembele.

"We should not forget that some of those in our team are A-youth players." Tuchel explained after the Ingolstadt match.

He added: "Even players such as Julian Weigl or Matthias Ginter, who are deemed to be experienced players, are still eligible to play at U21 level and are not used to the rhythm of Champions League, Bundesliga and then Champions League again. So we know why this is happening."

Youth and inexperience are not the only factors in Dortmund's patch of poor results, though. For instance, Tuchel had to field nine different backline combinations throughout BVB's last four matches due to injuries, lack of form and rotation -- not ideal for a defence looking to gain any kind of routine or stability.

But it also has to be noted that the starting XI fielded against Ingolstadt had an average age of 26.9 years. The fact that the likes of Pulisic and Passlack are grabbing headlines is also down to others not finding their feet.

Shinji Kagawa is one of the players currently falling short of expectations. The Japanese playmaker is yet to score or assist in either Bundesliga or Champions League play. Since his brace in a 3-0 win over fourth tier side Eintracht Trier in the German cup in August, his appearances have been mediocre at best.

That is simply not enough from the 27-year-old, who has to step up as his team endures a difficult situation. With the likes of Andre Schurrle and Raphael Guerreiro expected to enter team training this week, Kagawa failed to leave a lasting impression on Tuchel's doormat.

Against Union Berlin, Kagawa could receive another chance as Christian Pulisic and Ousmane Dembele are doubtful with illness. With Pierre-Emerick Aubameyang also doubtful and left-back Marcel Schmelzer and winger Marco Reus on the injury list, Tuchel's options ahead of the Revierderby against Schalke are limited.

Despite all the injuries, the 43-year-old hasn't made use of his entire squad just yet, as Nuri Sahin remains the only senior player that is yet to take part in a competitive match for Dortmund. When will Tuchel field the 28-year-old central midfielder, if not against Union Berlin?

Local newspaper WAZ titled "Sahin to bid farewell in winter" on Monday. While the club is fighting to extend Julian Weigl's contract, Sahin has fallen out of favour with his manager, who prefers to fill his bench with players that can play on multiple positions, leaving a specialist like Sahin out more often than not.

And it's questionable if Tuchel would even risk playing Sahin against Union, who sit second in 2. Bundesliga and arrive at the Westfalenstadion with the confidence of six wins out of the last seven matches. On top of that recent form, up to 12,000 Union Berlin fans are expected to travel with their team to create a worthy cup atmosphere.