Berbatov's third hat-trick of the campaign in Saturday's 5-0 win over Birmingham took the Bulgarian onto 18 goals, all but one of which have been scored in the Premier League.
It has been an invaluable contribution to United's 22-game unbeaten start, which has taken them top of the table with games in hand. Yet, in order for them to stay there, Ferguson knows that either Berbatov must continue at his present rate or his team-mates must start helping out.
Rooney is stuck on three goals, two of which came from the penalty spot, the same number as Ryan Giggs, Nemanja Vidic and Darren Fletcher, Javier Hernandez and Nani are the closest to Berbatov with nine and eight respectively.
"Dimitar is getting up towards that 20-goal mark, which is going to be important for us,'' Ferguson told Key103. "And hopefully we will get another one to that level too. Once you do that you know it is a substantial season.''
Rooney has struggled to hit the heights he achieved last season, when he scored 34 goals, but Ferguson is backing his out-of-sorts striker to hit the goal trail soon.
"We hope so, he [Rooney] deserves it. He is working his socks off and is playing some great football," said Ferguson, who went on to highlight Rooney's overall contribution in the triumph over Birmingham.
"The third goal was very, very exciting with the interchange between Berba and Rooney. It was right at half-time and it killed the match," Ferguson said. "Wayne showed fantastic control in the fourth goal to bring the ball from Edwin out of the clouds. The control of Rooney and setting up Ryan to square the ball for Berba - it was a fantastic goal."
But while Rooney continues to miss glorious opportunities, such as when he somehow headed wide from around two yards out against Blues, Berbatov continues to score and has now equalled Ruud van Nistelrooy's feat during the 2002-03 title winning campaign by netting three hat-tricks in a season.
The 29-year-old is also closing in on the five Alan Shearer scored in 1995-96, which remains a Premier League record, even if he is unlikely to match the seven Denis Law scored for United in all competitions during the 1963-64 campaign.
Not bad for a player plenty felt would be jettisoned by Ferguson last summer after failing to find top form in two seasons following his club record £30.75 million move from Tottenham.
"Dimitar is realising his ability,'' said Ferguson. "The other players sense it too. They are playing their part in playing with him. He has special qualities. I think we are using them.''