Change that to he needs to mature before playing "with the big boys" and you in in a nutshell remind me of Italy's problem in developing talent in last decade or more, where they have the mentality of lets put them into a "waiting" room until they "mature, instead of giving them a shot and see if they have what it takes. He is 19, shows he has talent, there is allways doubt and risk with young talents, but majority of top footie nations IMMEDIATELY give a young teeny talents playing time if they show promise.
FYI, not arguing against you, just reminded me as I said. Though Verratti isnt exactly typical example of this type of thing, even if its just Serie B, he has been playing senior footie since his 16th birthday.