Depth Only Concern After Borussia Dortmund Beat Sparta in Last Winter Friendly

Borussia Dortmund's final practice match before the restart of the Bundesliga on the weekend mostly confirmed what we already knew. As far as these friendlies go, that's not a bad thing at all—it shows that the team have a clear identity and don't have to experiment.

Their 3-1 over Czech outfit Sparta Prague—who've made it to the round of 32 in the UEFA Europa League, so they're not hopeless cannon fodder—was more dominant than the scoreline indicates.

However, there still remains one concern—is the squad deep enough?

In many ways, the win over Sparta was a fairly standard Dortmund game this season. Pierre-Emerick Aubameyang terrorised the opposing back line, scored a brace—the second was a real beauty, as the video below shows—hit the woodwork and should probably have added a third and even a fourth.

"

What a season Pierre-Emerick Aubameyang is having. 18 goals in the Bundesliga with this peach to boot #BVB pic.twitter.com/xWhkJ2NVGN

— CrowdScores App (@CrowdScores) January 19, 2016"

Henrikh Mkhitaryan scored his side's third goal off a rebound from a Moritz Leitner shot that hit the post, after the Armenian had initiated the sequence with a stupendous dribble.

Ilkay Gundogan amazingly kept his balance to assist Aubameyang's opener four minutes from intermission when he could easily have given up on the chance, and the Germany international bossed the midfield in the partnership with Julian Weigl that Dortmund supporters have come to love over the course of the season so far.

And since it was a standard BVB game, the Black and Yellows didn't keep a clean sheet, with Sparta's captain David Lafata temporarily equalising the game four minutes into the second half.

Matej Divizna/Getty Images

Dortmund left the visitors too much space, Mats Hummels was caught out of position after the ball ricocheted into Lafata's path and Roman Burki didn't have a chance to keep the 34-year-old's shot out.

Their prolific attack will likely have to cover up for their sometimes frail defence for the rest of the season, but that was already the case for large parts of the campaign so far and it worked far more often than not.

A more pressing problem doesn't revolve around tactics, rather a more mundane subject: As it stands, Dortmund's squad is a little thin. 

Injuries to Sven Bender and Marcel Schmelzer, who'll only return to team training this week after muscle problems, and the absences of Shinji Kagawa and Adrian Ramos due to illness—plus the long-term loss of Nuri Sahin—meant Thomas Tuchel didn't have many senior players left for the bench. 

After making nine substitutions during the second half—only Hummels and Burki had to endure the cold for 90 minutes—Dortmund's team was a blend of mostly back-up level defenders and academy products in the attacking positions.

Dortmund-based writer Stefan Buczko pulled out the calculator to make a keen observation:

That's not a problem for a meaningless friendly against Sparta five days before the first game of the Bundesliga after the winter break, but it wasn't a sight that will have eased the unrest among some parts of the Black and Yellows' supporters, who have taken to social media to voice their disapproval over Dortmund's transfer strategy.

When decision-makers Hans-Joachim Watzke (chief executive) and Michael Zorc (sporting director) made it known that Dortmund were looking to add players who'd take the squad to a higher level, via Jan Reinold of sport magazine Kicker (link in German), it raised expectations. 

Most fans would've been happy with a depth signing after Jonas Hofmann left for Borussia Monchengladbach and Adnan Januzaj returned to Manchester United earlier in January, but with those comments in mind, they dreamed bigger.

Boris Streubel/Getty Images

Dortmund still look intent to sign a player before the transfer window shuts on February 1, with Zorc telling German broadcaster Sport1 before the game against Sparta that the club are searching for a quality addition to the squad.

That addition could be Mainz playmaker Yunus Malli, whom we introduced as a potential target on the weekend. Bild reported on Tuesday that Dortmund and Malli have agreed on a contract and BVB have increased their offer for the Turkey international to €13 million (link in German).

Regardless of whether it's the 23-year-old or anyone else, it sure seems like Dortmund need to make a signing. With their current squad depth, they could be treading on thin ice.

Lars Pollmann is a Featured Columnist writing on Borussia Dortmund. He also writes for Yellowwallpod.com. You can follow him on Twitter.