It is his lack of goals - he has scored 13 in 66 Premier League appearances since his £6million move from Paris Saint-Germain two years ago - which drives his manager to distraction, even though he'd pay to watch him.
O'Neill said: "This lad, for the ability he possesses, should score double figures in a season. Into the penalty area, he's beating players and he should do better. He should finish them off, he really should for that ability because he can be mesmeric.
"When he dummies inside to come in, coming across the box, he should just drop the shoulder come inside and have the shot. He does it in training sessions time and time again. That's what I think. He scores in training.
"It's frustrating because this boy could be priceless if he could do that part of the game."