If Bayern Munich is to have any chance of a sixth straight semi-final appearance in the Champions League it will have to do something that only one team has achieved this season – defeat Real Madrid at Santiago Bernabeu Stadium.
Even a 1-0 victory on Tuesday will not be enough after a 2-1 first-leg, quarter-final loss in Munich.
Madrid's only loss in 23 games at the Santiago Bernabeu was in January, when Celta Vigo won 2-1 in the Copa del Rey. The rest were 17 wins and five draws.
"To try to win here we have to do the perfect game," Bayern coach Carlo Ancelotti said on Monday. "We will need to play with intensity, with courage, with personality. We will need to use all our quality."
In the Champions League, the defending European champions have been unbeaten at home in 12 consecutive matches, winning nine of the past 10.
"Our fans always give us a plus, especially in games like this one," manager Zinedine Zidane said.
Bayern has managed only two wins in 12 matches against Madrid at the Bernabeu.
"We'll go there and try to turn the tide," Bayern defender Philipp Lahm said. "It won't be easy, we're the underdogs."
Bayern's chances will be boosted by the probable return of forward Robert Lewandowski, who has recovered from a right-shoulder injury that left him out of the first leg.
"Lewandowski's presence will help us," Ancelotti said. "He's an important player who scores a lot of goals for us and he gives us more confidence."
Madrid had most of its regular starters available for the loss to Celta in the Copa del Rey quarter-final, where it couldn't come back after conceding two goals on counterattacks in the second half. Madrid was eventually eliminated 4-3 on aggregate after a 2-2 draw in Vigo.
"We will need to have a great game and be very strong," Zidane said. "We'll not gamble. The first leg is already in the past and we know the difficulties Bayern can create."
Madrid is trying to become the first team to defend the title since the competition's new format was created in 1992. Madrid defeated city rival Atletico Madrid in the final both in 2014 and 2016.
Only two teams have reversed a first-leg home loss in Champions League history – when Inter Milan eliminated Bayern in 2011 and Ajax got past Panathinaikos in 1996.
Bayern had been the dominant home team in the Champions League until last week's loss ended its run of 16 consecutive home wins.
"We come with a disadvantage but we are still alive," said Bayern's Xavi Alonso, who used to play for Madrid. "Hopefully we have corrected the mistakes that we made in the first leg. We need to play a very complete match."
Cristiano Ronaldo scored both goals for Madrid in the come-from-behind win in the first leg, becoming the first player to reach 100 goals in European competition. He is three short of the 100-goal mark in the Champions League.
The Portuguese forward was among the Madrid players rested by Zidane in Saturday's 3-2 win at Sporting Gijon in the Spanish league, a result that kept Los Blancos ahead of Barcelona in the standings.
Madrid forward Gareth Bale will not play on Tuesday because of a right-leg injury. Defenders Pepe and Raphael Varane also have been ruled out because of injuries.
Bayern teammates Mats Hummels and Jerome Boateng had been nursing injuries, but should be available to play, while Javi Martinez is out because of suspension.