Barkley started the season is dazzling form, but his performance levels appear to have dropped off in recent weeks.
The youngster has not been particularly influential over the past few months, as Everton’s season has petered out.
And Wilkins claims that, after watching Barkley play in Everton’s 3-1 defeat against Leicester City, he is now worried about the prospect failing to reach his maximum potential.
“I watched Barkley again at the weekend,” the former Aston Villa assistant said. “He’s got so much talent, but he’s not fulfilling it as well as he should be, I don’t believe.”
Barkley is still expected to go to EURO 2016 with England, where he is likely to be handed a key role by Roy Hodgson.
The 22-year-old is regarded as one of the finest prospects in the country, and he remains an integral player for both club and country.
Barkley has scored 12 goals for Everton this season, but he has not hit the back of the net in any of his last 13 appearances.
Barkley’s dip in form has contributed towards the Toffees’ poor sequence of results.
Everton have won just once in their last nine fixtures, causing them to slip down to 12th in the Premier League and exit the FA Cup at the semi-final stage.