He's a box to box, right? Will Gavi be the most defensively responsible?
Barcelona changed its formation to 4 midfielders, since then the team is more compact and comfortable on the field.
With possession Barcelona plays an asymmetrical formation.
..................... Ter Stegen
... Koundé..... Araujo..... Christensen
................ FDJ........... Kessie
.............................................................. Balde
.................Pedri.............. Gavi
Raphinha..........Lewa..
Balde has freedom and the entire left wing to attack. And when Baldé goes up, Kessie covers the band.
Pedri has more freedom of movement and is closer to the area.
FdJ can also carry the ball as he did at Ajax because he has Kessie guarding the position.
Gavi when pressing goes from the middle to the left wing.
Xavi found an ecosystem where each player is more comfortable and that improves the balance of the team.