He is still young, lots to learn, we can't go into next season with just Kane and Parrott. We do need someone who is a genuine backup and partner for Kane depending what system we play.
The age thing doesn't concern me as much as if he's genuinely deemed good enough.
IF he shows he is, then play him. If not, loan him out for a couple of years.
(Proving yourself in pre-season, as so often shown, is no proof at all.)
Thing is, we could have signed Piatek or W.Jose in January; no guarantees they'd have been any more productive than Jansen... There's always gonna be a degree of risk (vs. risk/faith in Parrot) unless you're buying talent proven in your league... Then you're talking price-tags beyond mere 'back-up' unless you're minted.
I mean, say we have 100m to spend in the summer... If we blow 50/60 on (eg) Calum Wilson/Mitrovic/Ings to warm the bench; we're not likely to see a great deal of improvement to our first XI.
If we can avoid spreading our funds too thinly; I'm all for it.
I want any likely big spend to be on a DM.