Frankfurt - The month of truth could end bitter-sweet for Bayern Munich and its star coach, Pep Guardiola.
Bayern is coming off a turbulent week in what Guardiola has called the decisive stage of the season. Guardiola's injury depleted team lost 3-1 at Porto in the Champions League quarterfinals. Then the team's doctor, Hans-Wilhelm Mueller-Wohlfahrt, quit after nearly four decades at the club, saying he and his staff had been unfairly blamed for the defeat in Porto.
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The mood improved somewhat after a routine 2-0 Bundesliga victory at Hoffenheim on Saturday in an efficient if not truly convincing performance, with some players being rested. Combined with other results, that victory could allow Bayern to clinch the league title the coming weekend.
First, however, Bayern has to try to overcome the two-goal deficit against Porto and reach the semifinals of the Champions League for the fourth consecutive year.
Here are some things to know ahead of Tuesday's match:
Bayern VS. history
Bayern has never overcome a two-goal deficit from an away leg in four attempts in European competitions. Most recently, it was eliminated by Chelsea in the 2005 Champions League quarterfinals and by Real Madrid in the 2000 semifinals.
Bayern's match at Porto was its 27th in the UEFA Champions League quarterfinals - one more than Manchester United, with whom they previously shared the record.
Porto, a two-time champion, is unbeaten on the road in this season's competition winning three of its five away games so far. Bayern has won all four home matches this season, with a 13-0 goal difference.
Guardiola is the middle of a three-year contract and won the domestic double in his first season but lost badly to Real Madrid in the Champions League semifinals.
Now, Bayern is threatened with an even earlier exit, which could shake Guardiola's so far untouchable position at the club. Although club officials insist the Bundesliga is the most important competition, Bayern is eager to repeat its 2013 treble season and add a sixth Champions League crown.
With Bayern's group of stars domestic dominance is taken for granted and Guardiola will be ultimately judged by Bayern's performance in the Champions League.
"I know that it's not enough to be German champion," Guardiola said, adding that "only a treble" mattered at ambitious clubs such as Bayern.
"When you win in a big club, you are a genius, a super tactician. When you lose, you have a lot of problems," Guardiola said ahead of his 100th match in charge in Bayern. His record is 78 wins, 10 draws, 11 defeats.
Bastian Schweinsteiger is back in training and could be available, along with Philipp Lahm, both victims of the flu. Franck Ribery is doubtful. Definitely out are Arjen Robben, David Alaba, Mehdi Benatia, Javi Martinez and Tom Starke.
"This match is like a final and it will be very difficult, but I have full confidence in my players," Guardiola said.
Lahm said Bayern was not in an "impossible situation."
"We are playing at home, we don't need to get nervous, we have 90 minutes to turn things around," Lahm added.
Forward Thomas Mueller said it would not be a "world miracle" if Bayern wins 2-0 at home.
Hundreds of fans turned out Sunday to give the Porto squad a rousing airport send-off. Supporters are dreaming of a repeat of the 1987 European Cup final, when Porto memorably upset Bayern 2-1.
Porto is unbeaten in the Champions League this season but in Munich its defense will weakened by the absence of suspended Brazilian full-backs Danilo and Alex Sandro.
"We'd be making a mistake if we went there to defend for 90 minutes. We'd never be able to do it," said Jackson Martinez, Porto's top scorer and team captain.
"We know it's going to be hard and we're going to suffer just like we did at home. But I think we have the right players for counter-attacks and we can deliver a good game."