The 25-year-old has had an inconsistent season with the Toffees due to a number of minor injuries, which has prompted the Belgian to call his playing time short during games.
"He's had a lot of niggles," the Liverpool Echo quotes Moyes as saying. "He's nearly not quite adapted to what the Premier League means and how the games go.
"I look at him and he's signalling to me with 15 minutes to go, so maybe he's not quite got what's required at Everton or the Premier League.
"What he has got in abundance though is pace, ability, he can score goals, he can take you on and he can play in two or three different positions."
Meanwhile, the Toffees have an outside chance of qualifying for the Champions League as they sit six points away from fourth place.