Manchester United legend Roy Keane isn't unconvinced by Anthony Martial.

The Frenchman scored in victory at Manchester City on Saturday.

After the derby, Keane says his belief was that United have already given the forward plenty of chances and that his inconsistency is a problem.

"The key for any player when you talk about a big club, you don't know what you're going to get with him, and they are no good for you. I wouldn't hang my hat on him," Keane said.

"I'm not convinced by him. He's had many chances, hasn't he? How long do you wait when you are Manchester United?"