United won the first leg 3-2 at the San Siro and Ronaldinho admits they face a difficult game.
“It will be a difficult match, but nothing is impossible,” Ronaldinho explained.
“I think it’s going to be a very beautiful match. We need a positive result so we’ll be playing for the victory and they’ll be playing at home with their own style because their Coach always makes them play that way.
“It has all the ingredients needed to be a great match. Milan have a strong tradition in the Champions League, so when Milan play in a competition like this everybody knows that Milan will be Milan.
“When I played for Barcelona we met them in the Champions League, so I know what it’s like to see the Milan shirt as an opponent.
“We knew they were a team with history and now I’m wearing the shirt I can feel Milan’s strength,” he concluded.