"Van Persie kept them on the back foot all the time," said Ferguson, who persuaded the striker to come to Old Trafford instead of the Etihad.
"His whole game was fantastic," added Ferguson after Van Persie's injury-time winner.
"City kept fighting," he said. "They kept battling and they've got this great record of scoring late goals.
"City scored a second goal and they deserved it. At that point, you're saying to yourself, 'I'll take the draw.'
"But up to that point, I thought we were far better than them."