German champions Bayern Munich were held to a goalless by Hertha Berlin in Bundesliga action on Tuesday. The draw could prove costly for the Bavarian giants who lead the Bundesliga table with 51 points if second placed Werder Bremen beat VfB Stuttgart on Wednesday, cutting their lead to 6 points. Goalkeeper Oliver Kahn salvaged the point for Bayern with a series of crucial saves throughout the match. Elsewhere, Egyptian forward Mohamed Zidan gave Mainz a 50th minute lead from the spot-kick before Arminia Bielefeld's Isaac Boakye equalized 7 minutes later to end the game in a 1-1 draw. In other matches, Borussia Dortmund beat Duisburg 2-0 and Kaiserslautern came from behind twice to hold Cologne to a 2-2 draw.