Look at the minutes each have played. Then take into account the games which Morata played on the wing as well. Mandzukic isn't all that prolific. He's been adequate. We all know Morata can score goals given the chance. Anyway, he ain't gonna start tonight but I hope he'll be first choice in a month or two like last season.
They've played more or less the same amount of minutes in the season and Mandzukic scored 5, Morata 3. Of course Morata is the better player but if in this moment Allegri chooses Mandzukic over him it's not out of the world, just see the performance of the two against Man City. If the coach is questioned about this kind of choices it means he doesn't get respect at all.
Yeah getting the hint he sees it mainly as balance thing. Cuadrado is subbed on for an attacker when Sandro is on the pitch, instead of Licht last was another hint.