The United striker has been sidelined with a calf injury since England's World Cup qualifier in Ukraine a fortnight ago and is unlikely to recover in time.
Ferguson still harbours a slim hope that Rooney will feature but his star forward faces a fitness race along with Scotland midfielder Darren Fletcher.
"On the injury front I can't give a clear picture, there are still some doubts about Rooney and Fletcher," Ferguson said.
Liverpool go into Sunday's match having lost four games in a row - the clubs worst run of form in 22 years - but Ferguson said that will count for little when the two arch-rivals clash.
"Derby games are derby games and anyone can win it," Ferguson said. "It has happened so many times and strange things can happen.
"I am not interested in their league form, I am more pleased with the kind of form we are in. We are consistent and consistent is important."
With Liverpool's star duo of Fernando Torres and Steven Gerrard unlikely to be fit for the United match, a loss this weekend could prove terminal for manager Rafa Benitez's ambitions on Merseyside.