He's played a ton, prior to this season. Don't pull a Hydde and act like he never plays. Barzagli almost exclusively played RB or in a 3 man CB line last year.
Rugani in all comps:
15/16: 1493 minutes (and all after December 13th. Didn't play a minute in the first 16 rounds of Serie A)
16/17: 1558 minutes (missed the last month of the season with a knee injury)
17/18: 2225 minutes (played the full 90 in 11 of our last 14 Serie A matches, including the last 4 rounds after Napoli loss - Inter, Bologna, Roma, Hellas - while fighting Napoli for scudetto)
Last season he was fantastic, and was our 2nd CB behind Giorgio (2162 minutes in league) in Serie A, playing 1935 minutes in the league. Allegri rotated well, as our first pairing was Benatia-Chiellini in CL, and Rugani-Chiellini in Serie A. Our record in Serie A with Rugani last year, by the way, 18 wins - 1 loss - 3 draws
The only place Rugani doesn't have a lot of experience is CL. But that will come with time. It's not like the guy is old. He's 24. And he's done a great job for us thus far in Serie A. Played matches against all of Inter, Napoli, Roma, Milan, Lazio, Fiorentina, Atalanta, etc. In Serie A we are 13 wins - 1 draw (only 6 goals conceded) against those teams with Rugani playing.