I wouldn't worry too much about Fratessi not starting yet. If you look at all the big clubs, the new buys are all starting on the bench, with the exception of ones that are directly replacing the players who left. There is only one game per week hence most coaches do not want to rotate.
Milan: Loftus-Cheek, Reijnders, Pulisic in place of Tonali/Bennacer (injured)/Saelemaekers (or J. Messias). Their most expensive player in Chukwueze has played less than 60 minutes so far.
Us: Thuram/Sommer in place of Onana/Lukaku (or Dzeko)
Napoli: None of their new signings are starting
Lazio: Kamada in place of Sergej
Juventus: Weah in place of Cuadrado, and Cambiaso has been starting in place of Kostic who looks to be a bench player now.
Roma: Parades in place of Matic. Aouar has started a few games, last one in place of L. Pellegrini who had an injury and another one as they sometimes play a midfield 3 instead of midfield 2 for most of last season.
Atalanta: New signing Bakker has 0 starts and Ruggeri has started every game. Scamacca and De Ketelaere just started their first game, but they also sold D. Zapata who was a starter (Hojlund also left). They do play Kolasinac as it looks like Toloi lost his starting spot.