If Nunez is out, it's the best possible news that arsenal could have had, I guarantee you Saliba and Gabriel would much rather face Liverpool without Nunez, the player who constantly runs in behind, competes for everything and pulls a teams defensive shape all over the place.
I think this is the toughest game we'll play until the end of the season, this is Arsenals cup final Sunday, they are gonna throw everything at it, if they lose then they can kiss goodbye to winning the title.