The German champions, who had won all eight matches in all competitions this season before their loss in Spain, take on third-placed Cologne on Saturday as they look to protect their three-point lead in the German league.
"It makes no sense turning this defeat into a major drama," Bayern CEO Rummenigge told players and coach Carlo Ancelotti at a post-game dinner.
"The only thing that is now important is that we react to this instantly, on Saturday against Cologne, to protect our lead at the top of the Bundesliga."
The Bavarians, chasing a record-extending fifth consecutive league title, are not expected to be thrown off track by the result but they must rediscover their killer instinct after also being dominant against Hamburg SV last week but leaving it late for narrow 1-0 win.
The German champions could not turn their overwhelming possession into goals, much like on Wednesday.
Few, however, doubt that Bayern will bounce back, with Ancelotti having no injury concerns in his large squad.
"It is a big disappointment but also a signal that we need to keep at it," Bayern midfielder Thomas Mueller said. "The areas we need to improve were highlighted tonight."
"We need to improve things and adapt to the tasks we have to master. We want to do it much better against Cologne on Saturday."
The visitors will be a tough nut to crack , however, having conceded just two goals in five games and having scored nine.
"We are brimming with confidence and we will gladly show it on the pitch this weekend," said Cologne defender Jonas Hector.
"We know it won't be the easiest game but we are looking forward to it because we are having a good run."
Bayern have enjoyed a winning start to the season with five wins from five league games to sit top of the table on maximum 15 points. Cologne are third on 11, with Borussia Dortmund on 12.
Dortmund, who twice came back to draw 2-2 against Real Madrid, travel to mercurial Bayer Leverkusen, who conceded a last-gasp equaliser at Monaco in their own Champions League group match and have so far managed just two league wins to lie in 10th on seven.
(Editing by Amlan Chakraborty)
