City lead the race for the fourth and final Champions League place and that adds fuel to the fire.
"It puts a definite emphasis on the derby game," Ferguson told a media conference on Friday.
"In my years at Manchester United this is the first time we have played City when they have had a chance to achieve something.
"A lot of neutrals will say that is fantastic for City and makes the game tomorrow more appealing than ever."
City manager Roberto Mancini said: "It is important because if we finish fourth we can change our path and play Champions League football next season. That is the most important thing, for the club, for the players, for me."
Ferguson said: "That's the great thing about derby games. In my 23 years every time we have played City, they have always said they would beat us. That's what derby games do, they create a fantastic enthusiasm and supporters want to hear that.
"It's a different derby game tomorrow because both teams can achieve something out of it ... and both can lose out of it as well."
United trail leaders Chelsea by four points with four games left and are desperate for a win. Fourth-placed City are just one clear of Tottenham with five matches to play and can afford no slip-ups, least of all at home.
Mancini said: "All derbies are important but this is especially important because United are playing for first place, we are playing for fourth and the two teams are very close."
With Wayne Rooney facing a late fitness test for United, the central on-field figure at Eastlands appears likely to be Carlos Tevez, the Argentine who has scored 28 goals for City since moving from Old Trafford last summer.
Mancini has described Tevez as the best player in the world at present, alongside Rooney and Barcelona's Lionel Messi yet, despite the striker's form, Ferguson has no regrets about allowing him to leave his club.
"No regrets whatsoever," he said. "We tried to buy him, we didn't match the money they wanted, the boy moved on. There is no bitterness from me, players leave here from time to time, some do well, some don't. We just have to move on."
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