Ferguson: Man Utd finishing was careless
Nani's 28th-minute goal was enough to claim all three points on an afternoon when United could have won much more comfortably.
Dimitar Berbatov missed a trio of glorious chances although Sunderland had their own opportunities before the break when John Mensah and Lorik Cana both headed wide and Steed Malbranque saw a well-struck drive turned over by Edwin van der Sar.
Ferguson added: "We were just careless in our finishing, I suppose. It looked that way. We had great chances.
"They probably felt they were comfortable but we got there, that's the important thing, three points.
"A 1-0 victory away from home is always a good result."