The Manchester United midfielder is due to sign for Napoli today.
Viviano told Radio Crc: "I expected Napoli to do better against Bologna, because (Antonio) Conte is able to express himself better when he has to sew a suit on the opponent.
"I go crazy for the fact that Manchester United let go of McTominay. I'm happy for Napoli, because he's a box to box like there are few. He is a player that Conte's team is missing at the moment."
Viviano also said of Juventus: "I expected Juventus to play like this, both for the coach and for the transfer market. (Manuel) Locatelli did very very well in these first two rounds: he will have space.
"It is the new ones who have to gain space, because he knows this way of playing football and is ready and prepared. In my opinion, (Teun) Koopmeiners will play further forward, but in any case there will be rotations. If (Dusan) Vlahovic doesn't play, we could also opt for a solution with Nico Gonzalez. I don't know if (Arek) Milik is part of the project."