Three impressive performances since his comeback have convinced his manager he is about to fire the goals United need to reinforce their Premier League challenge.
Ferguson, who takes his side to Newcastle today, said: "I think Rooney will explode again soon. He will start scoring, once he gets a few games back. We know that.
"His track record tells you that each year he gets better with his finishing. Rooney is fit. He trained really well during the period he was injured and that was the key to it.
"He maintained his fitness, which is important."