The Frenchman has even been left out of the starting line-up in some recent matches, but Petrov is convinced he will eventually win over his critics.
Petrov said: "A lot of people are on his back but we believe in him. We have seen in training what he can do.
"Sometimes people need a longer time to settle in. But we won't give up on this boy because he is an important player for us. He will come good.
"He has been working hard and is looking sharper.
"We have a talent here and it will come a point where he starts playing well and scoring goals.
"We are patient with him. He will come good."