City's two-point lead over their neighbours and confident mood on the back of three successive wins in all competitions has made the encounter less about local rivalry and more about title credentials.
Dismissed by Ferguson in recent seasons as a "small club with a small mentality" and "noisy neighbours," City will have been the first to notice the change in the way the Scot is viewing the fixture.
Asked if it was the biggest Manchester derby since he took over, United's manager told local media: "Yes, I think so.
"The last couple of years they [the derbies] have become more intense and there is more importance attached to them," added Ferguson who nevertheless views his club's fixtures with arch rivals Liverpool as the biggest games of the season.
"On Sunday it's top of the league against second top and it really builds up into a fantastic prospect for everyone. I am looking forward to that."
Roberto Mancini's side have averaged over three goals a game to go top of the table with 22 points from eight matches.
Both sides are unbeaten in the league and go into the match buoyed by their first Champions League victories of the season in midweek, City's coming after a stoppage-time winner from Sergio Aguero and United's thanks to two Wayne Rooney penalties.
"It will be a different game and different situation," said Mancini. "It is important to go there and do well because it will be very hard."
The pair have already met this season in August's Community Shield curtain-raiser, United coming back from two goals down to win 3-2.
Arsenal look to build on last week's win over Sunderland that lifted them into
