Yeah, it's actually an invaluable quality for a player to have - to look like he's not in the game for X minutes and then suddenly score from nothing.
Our other attackers are always noticeably in the game - even when Salah is triple marked he's only triple-marked as he's so obviously a danger, and so is affecting the game by his very presence, and drawing all the oppo's attention. Mane runs them ragged all the time and Bobby can be found in almost every position except keeper.
But Diogo is like a ghost, stealing around the attacking third unseen, slipping between the lines and through the cracks of the game and, like all the best phantoms, suddenly appearing from nowhere to scare the crap out of defenders and keepers, and make them cry out in terror and frustration as he slots one home and wheels away in celebration...