The Frenchman struggled to influence proceedings in the first leg last week, which Madrid won 1-0, but Guardiola has tipped the attacker to play a big role at the Allianz Arena.
"Franck Ribery is very important and necessary for us," Guardiola told reporters at a press conference.
"He has been at Bayern longer than me. I am happy of course if he plays well, with energy and motivation. He sometimes needs an angriness and I am sure he will play very well tomorrow.
"He has this fighting spirit. He always wants to fight, that's why the people love him. He is one of the most fantastic players in the history of Bayern."
Ribery has scored 16 times for Bayern this season.