Former Bayern Munich boss Ottmar Hitzfeld feels the return of Jerome Boateng could be essential to Pep Guardiola's Champions League hopes this season.
The 27-year-old suffered a groin injury in January and is not expected to be available again until April, meaning he faces a battle to be fit for the quarter-final and semi-final stage should the Bundesliga champions progress that far.
Boateng was left humbled by a brilliant solo goal from Lionel Messi during last season's semi-final against Barcelona, but Hitzfeld maintains the Germany international will be crucial to Bayern's chances of lifting Europe's top prize for the first time since 2013.
"It is not easy to miss that many defensive players," he told Omnisport. "Jerome Boateng especially is a huge loss for Bayern, he is their best defender. This might show, when they face Lionel Messi or Cristiano Ronaldo or Zlatan Ibrahimovic. This is when you need these special defenders.
"At the moment, Bayern are able to compensate by have a lot of possession. They can keep the danger away from their own goal, by pressing very high. But when the big opponents come around, like Real Madrid and Barcelona, who are strong with counters, you need a strong defence."
Bayern face Juventus in the first leg of their last-16 tie on Tuesday and Hitzfeld is backing the Bundesliga leaders to prove too much for the Italian champions.
Indeed, the former Switzerland national team coach says Guardiola's side have yet to hit their full potential this term given the relative ease with which they lead the standings in Germany.
"Besides Bayern Munich, there are Real Madrid, Barcelona and maybe Paris Saint-Germain as favourites. These are the four teams who look the best at the moment in the entire continent of Europe," he said.
"But of course, Bayern Munich belongs to the inner circle of contenders for the title. Bayern reached the final or semi-final in all of the last seasons. They have a great team and coach with Guardiola, who wants to finish his time with Bayern with the Champions League title.
"When they reach the quarter-finals and semi-finals, there are a lot of factors. Luck or the number of injuries might decide it. But for the upcoming match against Juventus I am confident that Bayern will reach the next stage.
"I think Bayern haven't reached 100 per cent yet. They have had some problems, due to injuries. It is an achievement for Guardiola, that the defence still seems stable, even while missing a lot of key players.
"But when the big games come around, they will be in top shape. Against Juventus, the available players in the defence should be enough."
Hitzfeld has backed Arturo Vidal to prove key in the encounters with his former side, describing the Chile international as the equivalent to former Bayern and Netherlands enforcer Mark van Bommel.
"Arturo Vidal is a fighter, who doesn't know any friends on the pitch," he added. "He is an aggressive leader like Van Bommel before him.
"He is important in close matches, where you might need to show your opponent how aggressive you can be. That's where Vidal will be needed. He had some problems with injuries, but when he is fit, he will be a boost for Bayern."