FRANKFURT, Germany (AP) -- Bayern Munich has a chance to become the first club to win two straight titles since the Champions League formed in the 1992-93 season.
Bayern, however, is the only team to have conceded a goal in the first leg of the semifinals after losing to Real Madrid 1-0. Chelsea held on for a 0-0 draw at Atletico Madrid and will look to clinch its second final in three seasons at home Wednesday.
Here are five things to know ahead of the second-leg semifinals:
ATTACK MODE I: Real Madrid has honed its attack for the trip to Germany. Besides winning the Copa del Rey over Barcelona two weeks ago, Carlo Ancelotti's side has stayed in the Spanish league title hunt by winning its last four games by the combined score of 17-0.
Cristiano Ronaldo scored his 46th and 47th goals of the season in all competitions on Saturday as Madrid crushed Osasuna 4-0, while also resting Gareth Bale as he recovers from the flu, striker Karim Benzema, defender Pepe and midfielder Xabi Alonso. Ancelotti said that Ronaldo is back to full fitness since a recent leg injury and that he expects both Bale and Benzema to play against Bayern Munich.
The Italian manager said he plans to go for the win instead of trying to make good on his team's slender 1-0 advantage. ''We want to score, not just defend,'' Ancelotti said. ''There is a good vibe in the team, a lot of confidence, and we are very motivated to play the match.''
ATTACK MODE II: Bayern was also in scoring mode at home, when it put five past Werder Bremen in the Bundesliga. But it also conceded two and trailed twice after playing a very poor first half. Bayern's defense looked vulnerable against counterattacks - precisely the way Madrid scored in the first leg.
Coach Pep Guardiola said the win was ''good for the mood'' before Tuesday's match, but did not hide his disappointment at how Bayern played in the first half.
Attacking midfielder Thomas Mueller was pragmatic. ''This game is not important but the mood is important and we need to make sure we release all our positive energy now,'' he said.
What should worry Bayern is its sudden weakness in defense - it has conceded eight goals in its last three Bundesliga games at home.
BAYERN VS. REAL: Real Madrid has nine European Cup titles, while Bayern is a five-time champion. The two clubs with the most titles have met in European Cup semifinals five times, with Madrid coming through only once, in 2000. In the most recent tie, Bayern won on penalties in 2012.
Madrid knocked out German opposition, Schalke and Borussia Dortmund, in the previous rounds, but it has only two wins in Germany with 19 defeats and six draws. Bayern has eight wins against Madrid at home, with one draw.
CHELSEA AMBITION: The only trophy Jose Mourinho didn't collect in his first spell as Chelsea manager was the Champions League, and it's the competition he wants to win at the end of his first season back. Not that there is much of a choice, as it still trails leader Liverpool by two points in the Premier League despite beating its rival 2-0 on Sunday.
Mourinho claims that finishing the season without a trophy won't trouble him.
''When you give everything you have, when you try everything, when you work hard, when the group is good, when the group respects the club and the fans, you wait for the end of the season and you see what destiny has for you,'' Mourinho said.
Mourinho has long insisted this was a season of transition.
Frank Lampard and Jon Obi Mikel are suspended for the second leg, while first-choice goalkeeper Petr Cech has been ruled out after injuring his shoulder in Madrid. Mark Schwarzer, the 41-year-old Australian who protected the 0-0 draw in the first leg, is set to stay in goal for the home fixture.
''He knows everything about the goal, about the small box,'' Mourinho said of Schwarzer. ''And when you are choosing a second goalkeeper you need to choose somebody that is especially mentally ready to play in any moment.''
WINNING FORMULA: Atletico Madrid's 1-0 win at Valencia on Sunday may have also served as a rehearsal for what it will hope to achieve at Stamford Bridge. Atletico continued its march toward the Spanish league title by again deploying a suffocating defense while getting the most out of its limited scoring chances. While a draw with goals will be enough to send it through to the final, Atletico will surely need to show the same poise at the back that it has demonstrated all season.
Atletico can also take heart that Chelsea has lost two of three European ties after drawing 0-0 away in the first leg.
''We are competing at the highest level and we hope to take another step for us and the history of the club,'' said midfielder Raul Garcia, Atletico's scorer at Valencia. ''We will have to play our hearts out.''