He said: "Since leaving Chelsea, this will be my first time back in England since I left in September 2007.
"I've not even been to my lovely house in London. Nothing. I've not even been shopping.
"So, it will be emotional to go back to England. I will be in the stands at Old Trafford but I probably won't even see anyone from Chelsea after the game.
"I will watch the people I love, the people who I have a great feeling for, but probably won't speak to them. I still believe Chelsea are in a great position.
"They are in the last 16 of the Champions League so anyone can win from the last 16. They are second in the Premier League. Chelsea was my team and it was my passion and it was not easy for me to leave them behind.
"Without Chelsea, it is easy because I love it here. I could stay here for a long time, the passion will be there.
"But I still see Chelsea from a long way away. I want them to succeed but it is not my team anymore. Bosingwa, Ivanovic, Anelka and Deco are not my players.
"My focus is on United and I will be at the game on Sunday to watch them. I'll do my preparations and after that I will have them watched by my scout."