Barcelona's Argentinian forward Lionel Messi gestures during a training session at the Luz stadium in Lisbon on Aug 13, 2020 on the eve of the UEFA Champions League quarter-final football match between FC Barcelona and Bayern Munich. (RAFAEL MARCHANTE / POOL / AFP)

BERLIN - Bayern Munich midfielder Leon Goretzka is convinced it takes 11 bravehearts to stop Barcelona superstar Lionel Messi.

Messi's qualities to enter the box from the wing to the middle, going past the full-back and the left-sided central defender is an open secret

"Thousands of footballers have been puzzling over this question and have tried to find an answer," the German international said ahead of the Bavarians' UEFA Champions League quarterfinal clash against Barcelona this Friday in Lisbon.

More than ever, the struggling Spaniards seem to depend on the 33-year-old providing inspiration and goals.

The Spanish newspaper El Pais wrote: "In uncertain times there is only one certainty: Messi."

Taking the 2019 FIFA World Player of the Year out of the game has become Bayern's primary target.

"One is not enough. It takes the entire team to work on it, keeping a cool head and not losing control," Goretzka added.

ALSO READ: Barca back to work ahead of Champions League quarterfinal

Helping his players stay calm is the job of Hansi Flick. The 55-year-old came up with an unusual training method to prepare his squad for the mammoth task.

The Bayern coach covered the training pitch with 30 squares, setting up individual orders for all spaces.

The 2013 treble winners seem to be looking to try to interrupt passes to Barca's central midfield, where Sergio Busquets waits to drive his side's game forward to find Messi.

Not only will Goretzka and Thiago Alcantara have to keep a close eye on Busquets and his midfield teammates, but so will attackers Thomas Muller and Robert Lewandowski.

On Bayern's left, rookie Alphonso Davies and the experienced David Alaba act as a double protective wall to go toe-to-toe with Messi.

Messi's qualities to enter the box from the wing to the middle, going past the full-back and the left-sided central defender is an open secret.

Barcelona's current crisis seems to have triggered the Argentinian's determination in a new way.

The four-time Champions League winner "has what may be no other footballer has: he can decide a game on his own," Bayern chairman Karl-Heinz Rummenigge commented, adding that Bayern must spoil Messi's zest for football.

Former Barcelona player Bernd Schuster is convinced Messi has to rescue the club's poor season, after they were beaten to the Spanish La Liga title by rivals Real Madrid.

"They need his goals to beat Bayern. Barca was never that dependent on him before," Schuster said after Messi secured victory in the last 16 against Napoli.

READ MORE: Feast of football awaits but no party time in Lisbon

Therefore, Bayern intend to close down all spaces with an intensive pressing approach, forcing their opponents to play long balls.

This might leave time to win back the ball and start counterattacks down the wings, with Muller supporting both sides and trying to link up with Lewandowski.

Goretzka seems optimistic things will work out for Bayern, with the midfielder set to face Messi for the first time in his career. "I've played against Ronaldo several times. I'm now very much looking forward to seeing how it feels to face Messi."