Robben believes if Bayern can silence Wayne Rooney they will beat Champions League rivals United.
He said: "This Manchester United team is not invincible.
"If the Press want to see them as favourites then that suits us because all the pressure will be on them. I have watched them on television many times recently and their team is certainly not as powerful as it was in the last two years. Rooney has been phenomenal this season.
"But at the moment he seems to be their only solution: What about if he doesn't function?
"He has become the star of the side since the sale of Ronaldo last summer but we will be prepared to stop him.
"They are almost a one-man team so our defenders will give him 180 minutes of non-stop distraction."