Barcelona are now "more dependent" on talismanic forward Lionel Messi "than they have ever been", according to Bernd Schuster.
Despite missing the start of the 2019-20 campaign, Messi finished the domestic season as the top scorer in La Liga, winning the coveted Pichichi award for a record-breaking seventh time.
The Argentina international has hit 31 goals in 43 appearances in all competitions, with his latest effort coming during a thrilling Champions League win against Napoli last weekend.
Messi jinked his way through the Italian outfit's defence and picked himself up from the floor before curling an unstoppable strike into the far corner of the net, with Clement Lenglet and Luis Suarez also getting on the scoresheet to seal a 3-1 victory at Camp Nou.
That result saw Barca progress to the quarter-finals 4-2 on aggregate, and they are now scheduled to face Bundesliga champions Bayern in Lisbon on Friday for a place in the last four.
Schuster says his old club, who surrendered their La Liga crown to Real Madrid in July, have become far too reliant on Messi in recent times, and has warned that they will struggle to beat Bayern if the diminutive magician is off his game.
"Barcelona are more dependent on Messi than they have ever been," the ex-Barca midfielder told Bild.
"Messi can still win games on his own. He has the quality to score goals against Bayern and decide the game on his own.
"There are only two options for Barcelona this season, that Messi scores the goal or that they have a world-class day in the game without the ball."
Pressed further on the challenge Bayern will pose Quique Setien's men, Schuster responded: "The way they have played so far and won the championship, they are one of the favourites for me."
The 60-year-old went on to express his belief that Atletico Madrid, another of his former clubs, are well placed to reach the semi-finals of this season's Champions League at the expense of RB Leipzig.
"The final is definitely a size too big, but what they have achieved so far is excellent," Schuster added on the Bundesliga side's run to the last eight. "You have to see what a young and sometimes inexperienced team they have.
"And that is at the Champions League level! Atletico are old cannons who have been playing at the top level for years, and have been in the final twice.
"Leipzig also has the disadvantage of having lost Timo Werner in this situation."