The Ivory Coast star is looking for a Manchester double tomorrow by following up two Premier League goals against City with some FA Cup strikes at United.
Williams said: "The game on New Year's Day was the best he has performed for us. I am really pleased for him. His two goals were the big positive we took from a defeat.
"Hopefully now he can keep his place in the team and we can give him that confidence to know he's wanted. We can build our game around him."
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