The way I see it, he picked up a knock for the Azzurrini (therefore not on the bench vs Udinese), and there was no place for him on the bench vs Zenit - not to say never, but it is our first CL game after two years against a very good side - gambling his inexperience isnt something Ranieri would want to do. Of course theres always the possibility he would succeed, but football isnt that easy.
Which leaves Cagliari as a deadline.