Pep Guardiola conceded that Bayern Munich are enduring a difficult period, but stressed he remains “optimistic” about his side’s chances of reaching the last four of the Champions League. Bayern were left stunned by a 3-1 defeat to Porto in the first leg of their quarterfinal last week, meaning the German champions will have to win by at least a two goal margin at the Allianz Arena on Tuesday to book their place in the semifinals for the fourth successive season.

The fallout from the first leg defeat has been considerable. The club’s long-time doctor Hans-Wilhelm Muller Wohlfahrt left his post complaining that the medical team had been blamed for the surprise defeat in Portugal. The friction comes as Bayern continue to battle a lengthy injury list. Arjen Robben, Franck Ribery, David Alaba, Mehdi Benatia and Javi Martinez all remain sidelined, although Bastian Schweinsteiger could return from an ankle injury.

The fine margins between success and failure at a club where domestic dominance is now taken for granted mean that the first-leg loss has also led to much discussion about Guardiola’s own future beyond this season. He has insisted, though, that he will see out the remaining year of his contract next season, and fully accepts the pressures of being at one of Europe’s giants.

“The game is a big challenge, but when you're coach of a club like Bayern every day is a challenge,” he said, according to UEFA’s official website. “During the last few weeks, which have not been easy for us, I have learned a lot about my work.

“I am very satisfied being coach of this club. Even with all the problems we have, we are in the semifinals of the German Cup, we will probably retain the German title and we are still in the running in the Champions League. But I know the club I am working for. It is like in Barcelona or [Real] Madrid -- only the treble is enough.”

Bayern beat Hoffenheim 2-0 on Saturday to go 12 points clear at the top of the Bundesliga with just five matches remaining. That score line would also see Bayern advance against Porto on Tuesday, and Guardiola is hopeful his depleted squad can deliver a required result.

“Tomorrow we have to take more risks,” he said. “That is normal after the game in Porto. I am optimistic and realistic. After a 3-1 loss in Porto, it will not be easy at all, but I am optimistic we will go through to the semifinals.”

Porto are now on the verge of reaching the Champions League’s final four for the first time since they upset the odds to win the competition in 2004. They have again shown themselves to be impressive European campaigners this season, having topped their group before easing past Basel in the Round of 16. In the first leg of the quarterfinal they caught Bayern cold with the intensity and selectiveness of their pressing to go 2-0 up in the first 10 minutes through two Ricardo Quaresma goals. Jackson Martinez then added a third following Thiago Alcantara’s sole response for Bayern.

The prospects of Julen Lopetegui’s side finishing the job in Munich have been dealt a blow, however, with suspensions ruling out both first-choice full-backs, Danilo and Alex Sandro. Lopetegui, though, insists neither the absentees nor the score line in the tie will impact Porto’s approach.

“Of course we'll have to make some changes, but the way we approach the game will remain the same,” he said, reports “We are a team without any big surprises and quite predictable: when we have the ball we want to attack; when we don't have the ball we want to get it back. I don't waste energy and time thinking about what Bayern will do. We need to focus on ourselves.”

Probable Lineups

Bayern Munich (4-3-3)
G: Neuer

D: Rafinha, Boateng, Dante, Bernat

M: Lahm, Alonso, Thiago

F: Müller, Lewandowski, Götze

Porto (4-3-3)
G: Fabiano

D: Ricardo, Maicon, Martins Indi, Marcano

M: Herrera, Casemiro, Óliver

F: Quaresma, Martinez, Brahimi

Kickoff time: 2:45 p.m. EDT

TV channel: Fox Sports 2

Live stream: Fox Sports Go, Fox Soccer 2Go,