PIRAEUS (Greece) • German football champions Bayern Munich will be stepping on the gas against Olympiakos in their Champions League group-stage opener in Piraeus today, hoping to kick off their European campaign with a performance worthy of a title contender.

Bayern coach Pep Guardiola, in his third season in charge and still chasing his first European crown with the German side, was unhappy with his team's last-gasp 2-1 win over Augsburg in the Bundesliga on Saturday. He has called for a quicker, more focused game against the Greek champions.

The Bavarian side needed a 90th-minute penalty from Thomas Mueller, a controversial decision that referee Knut Kircher admitted later was a mistake, to edge out their opponents and maintain a perfect start to the season.

"We cannot allow that to happen," said forward Robert Lewandowski. "It will not be an easy game in Greece and the atmosphere there is fiery. We have to play very well from the start and not from the 46th minute as we did against Augsburg."

"We need to step more on the gas," added the Poland striker , with Bayern also due to play Dinamo Zagreb and Arsenal in Group F.

Bayern, who won the last of their five European Cups in 2013, will be without wingers Arjen Robben and Franck Ribery.

Douglas Costa, in fine form since joining them in the close season, is again expected to start on the left.

Teenager Kingsley Coman is also an option after the talented Frenchman came on as a substitute for his Bayern debut against Augsburg.

Central defenders Medhi Benatia and Holger Badstuber will miss the game through injury, with Javi Martinez likely to be included in the squad after recovering from a year-long ligament injury.

Bayern's big-name absences mean little for Olympiakos, who are well aware of the monumental task ahead. "I do not think we should talk too much about the players missing because it makes no difference. There is so much quality in their squad," said their Norwegian defender Omar Elabdellaoui.

The Greek title holders, who have won their last six home fixtures in the Champions League, have also reinforced their squad, bringing in experienced former Argentina midfielder Esteban Cambiasso.

"We need to focus on our work. We believe we can get something out of it because if you don't believe, then you have already lost even before the game," said Elabdellaoui.

REUTERS