Spurs go into the game on the back of last week's defeat to Wigan Athletic.
"If you win at United, you can win anywhere and not just in England, anywhere in Europe," Defoe told Spurs TV Online.
"They are one of the biggest clubs in the world and to go there and play how we did in the first half, that performance was unbelievable.
"The second half was a little different, but you get that at Old Trafford. If we can do the same at City it would be fantastic."