Shaky Dortmund worries Tuchel before Benfica match

Berlin - Thomas Tuchel admits Borussia Dortmund's shaky defence is a concern ahead of Tuesday's Champions League clash at Benfica after crashing 2-1 at bottom side Darmstadt in the Bundesliga.

Dortmund suffered its fourth league defeat this season on Saturday to leave it fourth in Germany's top flight - 15 points behind leader Bayern Munich.

It was far from the ideal preparation for Tuesday's last 16, first-leg, away match at Benfica as Dortmund failed to take its chances and was too loose at the back.

Dortmund striker Pierre-Emerick Aubameyang, the league's top scorer with 17 goals, managed just two shots on goal in 90 minutes.

"It was a confirmation of what we have been showing this season," said Tuchel of Dortmund's performance.

"Darmstadt were much closer to 100 percent than we were, they deserved the win.

"We were well below our potential, the fact we showed so little of ourselves out on the pitch is bitter enough."

Tuchel named three teenagers in Dortmund's starting line-up.

Dzenis Burnic made his debut in defence, the second 18-year-old in the starting line-up alongside U.S. international midfielder Christian Pulisic, while attacking midfielder Emre Mor is only 19.

Neither Mor not Bunic played well, but Tuchel furiously defended the teenagers.

"I almost forbid these two names to be linked to the defeat," he fumed.

"It would be vile to blame them for it in anyway, they have nothing to do with it."

Tuchel started with central midfielder Shinji Kagawa, plus wingers Ousmane Dembele and Andre Schurrle on the bench, but his selection backfired.

Darmstadt went ahead on 21 minutes when U.S. international striker Terrence Boyd, on loan from RB Leipzig, netted having been left unmarked in the middle.

Dortmund's Germany winger Marco Reus hit the crossbar from a free-kick on 32 minutes before midfielder Raphael Guerreiro levelled with a bullet shot just before the half-time break.

But Darmstadt sealed the win - its first at home since October - when Boyd's replacement Antonio-Mirko Colak got in behind the defence and slotted his shot between Dortmund 'keeper Roman Burki's legs.

"It's difficult to put into words," said Burki, whose defenders left him exposed before he leaked the winning goal.

"It was very unusual that I faced so many balls in front of goal," he added having had to deal with 15 shots on goal.