I get the Duff comparison, but whereas Duff had a ton of talent but never developed the ability to run a game with his passing and technique, I believe Doak has the coaches around him to become a much better all round player.
All this talk of signing an attacking player to cover for the Diaz/ Jota injuries is nonsense to me: give Doak a chance!
Between now and the return of the aforementioned, he can learn a lot, and contribute a lot. If you're good enough, you're old enough, right?