Arsenal boss Arsene Wenger rates Bayern Munich as Champions League favorites.

Wenger admits it is impossible to argue against Bayern being the world's best on current form and knows there is a small margin for improvement.

"Last year they won the German league, the German Cup, the Champions League and the (Club) World Cup," he said.

"Maybe in the style there is always room for improvement but if they just do the same achievements this season they can say they have improved, because it's more difficult to do it again."