Araujo is expected to be out for 6 to 8 weeks which is definitely very difficult for Barcelona in defense.
Pique is still able to play but at his age I would probably prefer Christensen to be brought in as a defender there.
But it's not impossible for Pique to be able to play because despite his unfinished conflict there, Barcelona still need him even if it's only a rotational player.
Pique was in the squad list that Xavi brought to Mallorca, so I think Xavi can also give him a chance considering Araujo is currently injured. Crhistensen and Eric Garcia also seem ready and fit to play in defence against Mallorca, they were also in today's squad but all the decision rests with Xavi. So for this match I don't think Xavi will have a big problem as a result of Araujo's injury in defence, but because Barcelona have a very busy schedule in October I really feel Xavi has to be careful in choosing players in some easy match.
Lewandowski, Dembele and Raphinha are also available in this match, so I hope there are no problems with the strikers so I can expect Barcelona to win this match against Mallorca. But whatever the current state of Barcelona, we will see how they overcome this during October especially when they have to play some tough matches against Inter (2x), Real Madrid, and also Bayern Munich. October schedule is very tough for Barcelona, so Xavi must really be able to prove the quality of his team and keep his form good.