Maybe you would expect top, top players to be knocking on the door around 18 - Rooney, Barkley, Lampards and Gerrards etc, but even then only a few mins here and there generally. Plenty of other very good players won't have made their debuts or really started to become full time part of the squad until a few years later. It's only really about 21 imo that you have to start thinking about whether they are going to make the step up, and even then some will develop later than that.
With this new contract and the move to playing as a striker, he's certainly on the right track...