Aston Villa boss Martin O'Neill remains confident Stilian Petrov will find his best form in the Premiership.
O'Neill said: "Stilian is a very good player but I've seen little spells before where he was also lacking in confidence at Celtic.
"He wants to do well but the early chance he had against Newcastle showed how he is feeling at present.
"The Stilian Petrov I know, the fully confident one, when someone laid the ball back to him in the outside right position, would not have whipped in his shot first time and miscued it.
"A Stilian Petrov with confidence wouldn't have done that. I know what he is capable of. He's scored goals for Celtic, including goals at European level.
"Yes, I'm asking him to play a different role at the moment but it's something that he is going to have to live with."