The summer signing from Wolverhampton Wanderers bagged his fifth goal in five games at the Stadium of Light to earn the Black Cats their first win of the season.
"His display was incredible," O'Neill told BBC Sport. "He held the ball up and gave space for the others and when you are relying on him to get into the area, he does that. He has been terrific for us and long may his run continue."
The three points have moved Sunderland up to 13th in the Premier League table.