Robben has been rooting for Chelsea to prevent United lifting a fourth straight domestic title.
And, after missing last week's 2-1 first-leg win, he hopes to help bundle Alex Ferguson's men out of Europe tonight.
Robben, 26, said: "Chelsea are my old team, so I have been watching them in the title race, but now my focus is on this game with United.
"The atmosphere will be great, it always is at United.
"We weren't ready in the first minute in Munich but we will be ready this time. We know we have a chance."