Five days after winning the German Cup against Borussia Dortmund with 2-1, Ribery put Bayern ahead in the 18th minute, albeit with a little luck.
The French international first failed to convert a penalty shot against Zenit keeper Wjatscheslaw Malafejew, only then to see the ball role in.
Dominant in the first half, Bayern failed to capitalize on their strong start against Zenit, who eliminated German soccer powerhouse Leverkusen.
The lack of coolness displayed by suspended Luca Toni was clearly lacking in many scoring opportunities, and Miroslav Klose and Lukas Podolski were hardly able to step up to the task.
Bayern were punished during the second half.
In the 60th minute, Zenit equalized with the help of Bayern. A pass by Russian midfielder Wiktor Fajsulin was redirected at Oliver Kahn who couldn't hold onto it.
In the 83rd minute, Fajsulin even had the chance to win the match had it not been for Ze Roberto who cleared the ball shortly before the line.
The German title holders and 1996 UEFA Cup winners now have to win in St. Petersburg or at least score two goals in case of a draw in order to reach the finals on May 14th in Manchester, wherethey would face the winner of the Glasgow Rangers vs. AC Florenz match.
"We will have a harder job in St. Peterburg," Bayern coach Ottmar Hitzfeld told the press after the match.
However, Zenit coach Dick Advocaat told the press conference that they would "have more problems" since Arschawin, Ricksen and Radek Sirl are suspended for the upcoming match in St. Peterburg.
