Both hitmen are in contention for a start against Norwich on Saturday and the boss believes they could eventually eclipse the achievements of Dwight Yorke and Andy Cole, who helped fire the Reds to Treble glory in 1999.
Although the manager is spoilt for choice in attack, he believes Hernandez is bound to increase his tally in the near future.
"They're an immense goal threat," he said of Rooney and Hernandez. "The boy Hernandez is coming back and he's only scored two goals so far so I expect him to score 25 goals or more.
"Wayne's had a fantastic start to the season so the capabilities are there. You always miss great players like him but we've got a squad that is good enough. I've got Danny Welbeck, Michael Owen, Dimitar Berbatov, Federico Macheda and Mame Biram Diouf. It is such a strong unit.
"Danny always had ability as a kid but growing up and getting stronger brought it's own problems and he had niggles with his knees. A series of injuries derailed him so he wasn't considered for the England squad but he is now and his opportunity will come."
The manager admits that Yorke and Cole are always going to be a tough act to follow in terms of strike partnerships at Old Trafford.
"Yorke and Cole got 52 goals between them and it was Yorkie's first season," he recalled. "I think Yorkie was probably one of the best strikers in Europe during that first season here.
"It was amazing. He and Andy hit it off immediately. I'd like to hope Rooney and Hernandez can outscore them but you never know as it's a tough