Bayern Munich chairman Karl-Heinz Rummenigge has backed Franck Ribery to make his comeback before the turn of the year.

The ex-France international has been out of action since March due to ankle and back problems and it remains uncertain when exactly he will return to match action.

However, Rummenigge remains optimistic that the 32-year-old will soon be back, even though he has acknowledged Ribery could still be unavailable for a number of weeks.

"I have no doubt about it that Franck will return to the pitch this year," Rummenigge told TZ.

"The first thing we need now is an exact diagnosis of the problem. It could still be a while, though."

Rummenigge then went on to discuss Bayern's Champions League match versus Olympiacos on Wednesday and warned that the Bundesliga champions cannot afford to take their opponents lightly.

"We cannot underestimate this group and Olympiacos. Big teams like Borussia Dortmund and Manchester United have already had some tough games here," he continued.

"But an experienced team like ours should keep their heads cool."

Bayern also face Arsenal and Dinamo Zagreb in Group F.