Lehmann believes his old club will face a real challenge to progress further in the competition against last season's beaten Champions League finalists.
Writing in a column for the Sport Bild magazine, Lehmann said: "For an English team it is the worst draw to play a German team directly after the winter break.
"In addition to that Bayern has not been really challenged for once yet in the second half of their season. The only stress they have is the one at the training sessions."
However, Lehmann, 43, believes Arsenal have the players to cause Bayern problems.
He added: "(Bayern coach) Jupp Heynckes will warn his players of the speed that Arsenal still can play in the offensive game, especially Theo Walcott but also more and more Lukas Podolski can be very dangerous.
"Vice-versa, Arsenal will look to stop Bayern creating their good positioning game from which they can accelerate."