Lahm has claimed the difference between Arsenal and his team is "enormous".
He said: "The difference between the clubs was enormous. Arsenal were not brilliant because they never had chances. Bayern was the owner of the game and the first goal changed the situation.
"Now Arsenal will have to show a strong reaction and, even though we are very confident, we know they will try to show some pride and play well.
"But if we don't obtain qualification it will be a disaster. That would be the biggest failure of the season."