The Bulgarian has not scored since his stunning hat-trick against Liverpool in September.
“In fairness to Dimitar, we’ve been changing the strike partners quite a lot this season,” Ferguson said in the Daily Mirror.
“I have to accept responsibility for that.
“We’ve got a lot of good, young options who have played in a lot of games recently, players like Javier Hernandez, Federico Macheda and Gabriel Obertan.
“But Dimitar is suited to playing with Wayne. We hope we can get Wayne back to his best.”
Ferguson added: “There’s also the option of playing Wayne on his own, but the pair of them play well together.
“Playing is the name of the game for Wayne now.
“Wayne was very rusty on Wednesday (against Rangers). But when he took his penalty kick, he came to life. He played really well in that last few minutes. I think he enjoyed it.”
