I doubt we'll see a new formation this early in the season against a lower level opponent like Brescia. If anything, Sarri would make them play out of position in his formation to encourage players to gain comfort in the formation.
If those 3 midfielders are the best adapted to Sarri's system, why play them every match, even against minnows? If Matuidi is vital to the team, shouldn't he get a rest before the important matches? I know Sarri spoke about the obsession with rotation but that doesn't discount it is important. Pjanic also just came off hobbled in a match. And he came on as a sub the next match. Shouldn't he get another rest just to be sure?