BERLIN, Oct. 1 (Xinhua) -- Ahead of the UEFA Champions League group encounter against FC Copenhagen this Tuesday evening, Bayern Munich is grappling with unpleasant difficulties.

While the front line, fuelled by the goal hunger of England captain Harry Kane, has transformed into a well-oiled scoring machine, the defense has morphed into a wavering trouble spot.

Three conceded goals in the Champion League 2023-2024 campaign opener against Manchester United, followed by two in the Bundesliga against Leipzig, narrate a surprising tale not many anticipated.

Despite having invested 160 million euros plus bonus payments for Dayot Upamecano, Matthijs de Ligt, and Kim Min-jae, stability seems elusive at present.

The return of 35-year-old Jerome Boateng triggered unmistakable excitement among fans around the training pitch on Sunday, while others assert his best times are behind him.

For TV pundit and former Bayern midfielder Stefan Effenberg, it's far from a positive signal for the Bavarians to reactivate the club-less veteran despite his having won the Champions League twice in Bayern's shirt from 2011 to 2021. "It seems striking that they have missed out on something," the 55-year-old said.

While coach Thomas Tuchel is striving to fill the gaps by devising unexpected solutions like appointing midfielder Leon Goretzka as a central defender, the imbalance in the Bavarians' performance has alarmingly surfaced.

Midfielder Joshua Kimmich is complaining about the team's "inability to execute the 90 minutes in a constant way." Tuchel sarcastically mentioned, "the difference to last season is that the games don't entirely slip out of our hands."

Bayern has relinquished the league lead, trailing two points behind Xabi Alonso's Leverkusen and one behind VfB Stuttgart.

"It's far from a piece of cake to win the title as I expect Leverkusen, Dortmund, and Leipzig to give us a hard time," Tuchel said, while adding, "We currently act far too sloppy."

Hopes are now mounting for a victory in Denmark to gain ground in the Champions League's Group A and conserve energy for the demanding league fixtures.