Bayern Munich begins the defense of its Champions League title against CSKA Moscow with warning words from the club's sporting director ringing in the players' ears.

Unprecedented success last season has been followed by an underwhelming start under new coach Pep Guardiola - by Bayern's own lofty standards - prompting Mattias Sammer to warn against complacency ahead of the Russian league leader's visit on Tuesday.

Bayern is attempting to become the first team since 1990 to defend the European Cup.

''It's the nicest competition of the season,'' Guardiola said on Monday.

Czech champion Viktoria Plzen hosts Manchester City in the other Group D match, with the visitors aiming for improvement under new coach Manuel Pellegrini after crashing out in the group stages in the last two seasons.

Pellegrini led Malaga to the quarterfinals last season.

No team has successfully defended the Champions League since its inception in 1993 and Sammer hoped to provoke a reaction from his side to repeat last season's achievements.

''We're a bit lethargic, we play football without emotion, we're doing the minimum,'' Sammer said after Bayern's 2-0 Bundesliga win over Hannover on Saturday. ''That's not enough for the level of football that we want to play.''

Sammer pointed out that Bayern was beaten in the German Super Cup by Borussia Dortmund, ''gave away points'' in the Bundesliga to Freiburg, and was a referee's whistle away from losing the Super Cup to Chelsea - Javi Martinez equalized with the last kick in extra time to take the game to penalties.

''We have to get out of this comfort zone. Our coach has to let rip every time for us to get into gear. That's not how it works. We're all partly hiding behind the new coach,'' Sammer said, suggesting the excuse of adjusting from Jupp Heynckes, Guardiola's successor, was no longer relevant.

''I don't want to hear any discussions about systems or whatever. We just have to talk about a couple of basic elements, namely the emotion and passion to play football.''

Guardiola said Monday he was ''satisfied'' with his team's performances to date ''but we have to try and play over 90 minutes.''

The former Barcelona coach said only he was responsible for the players' performances - ''the players do what I tell him'' - and that he did not need support from Bayern's management to handle the team.

''I've noticed from the very beginning that Mattias, Kalle (Bayern chairman Karl-Heinz Rummenigge) and Uli (Hoeness, the Bayern president) supported me. Mattias is very emotional, like me, and after the game he can give his opinion. He's one of the most important people here,'' Guardiola said.

''I'm not surprised he gave his opinion. It's a cultural thing. It doesn't happen in Barcelona or Madrid. But people here are entitled to give their opinions. If you did that in Spain it would be a big problem.''

Hoeness had already provided the good cop to Sammer's bad cop routine on Monday.

''I'm also all for analytical criticism but I don't think the situation's so critical,'' Hoeness told German daily Bild. ''You get the feeling that we have to excuse ourselves for a dominant 2-0 win.''

In truth, Bayern looked far from dominant against Hannover until Mario Mandzukic's 51st-minute goal settled the home side's nerves.

Franck Ribery ensured Bayern extended its club record of 30 games unbeaten in the Bundesliga. It was also Bayern's 11th consecutive league win at home.

''Guardiola doesn't need to be supported,'' Hoeness said. ''I'm not worried at all.''

Bastian Schweinsteiger didn't play after failing to fully recover from the ankle injury that kept him out of Germany's World Cup qualifiers, while fellow midfielders Mario Goetze and Thiago Alcantara remain out.

''Basti is better, but Javi, Mario and the others aren't yet fit,'' Guardiola said.

The Spaniard is familiar with CSKA from his days as a player. He was part of the Barcelona team that surrendered its European Cup title in a loss at home to the Russian side in November 1992.

But CSKA has lost both games it played in Germany, at Hamburger SV and Wolfsburg. Bayern and CSKA have never met before.

The Russian club is returning to the Champions League after a one-year absence, making its fifth appearance in eight seasons.

''We have one aim, to go onto the pitch and try to win,'' CSKA goalkeeper Igor Akinfeev told the UEFA website. ''But if we can't do that, we'll play with our heads held high. You can't always beat the best teams in the world.''

Plzen is appearing in the Champions League for the second time in three years but has been weakened by the transfer of Czech Republic midfielder Vladimir Darida to Bundesliga side Freiburg.

Plzen midfielder Jan Kovarik said the game against Manchester City ''will be the biggest game of my career.''

The club leads the Czech league with 20 points from eight matches and is coming off a 1-1 draw at Liberec.

''It could happen that Manchester City will underestimate us,'' Plzen defender David Limbersky said. ''We'll see what happens on the pitch.''

City has made an inauspicious start to the Premier League, surprisingly losing to Cardiff and then being held to a disappointing 0-0 draw at Stoke on Saturday.

Captain Vincent Kompany could return from groin injury sustained in the first league match but City will likely have to cope without injured playmaker David Silva.