Smith has just returned to action from a broken leg suffered 14 months ago.
Ferguson said: “He has been absolutely unbelievable. His form in the last three games has been outstanding.
“He has brought a freshness and an infectious enthusiasm which is spreading throughout the team.”
He added: “When you think of what he has been through, how he has handled it and the way he is approaching his football, he has been first class.
“I cannot speak more highly of him than that.”