Firpo should not play in any position at Barcelona, he doesn't have the class
But it's a bit ironic that Koeman talked so much about playing players in their right position
Look at a game and Griezmann is both LB and CM as much as FW, Busquets has played B2B, Pedri plays CM, De Jong played CB (to my delight but still), Dest played LB, I've probably missed some things.