City left it until the dying seconds of last season before winning the title on goal difference ahead of United.
After adding the likes of Shinji Kagawa and Robin van Persie to the Red Devils, City boss Roberto Mancini tipped United to win back their league title, however Ferguson is adamant that their Manchester neighbours will be the toughest competition.
"We are favourites every week according to him, does he not realise he's got a decent team himself," joked Ferguson.
"That rivalry has been going on 100 years, not just last year, neighbours are neighbours and these games never change. But if you ask me who I think will be our biggest threat I would say Man City without question."
United get their Premier League campaign underway on Monday night as they travel to Goodison to face Everton.