Basically friendly games are not an indication, if we say "Barcelona lost to Monaco so they are not looking good", we could also say "Barcelona beat Real Madrid they are looking strong" which one makes sense to you, I personally do not think that we are going to make that much sense by just saying which one makes sense, it is not really that complicated to make that sense and we should not be looking at it like an important game, it's only just friendly games and we can't really make a deduction from it at all. We are going to face Barcelona doing decent enough but I still expect second place for them.
I don't think we can equate Barcelona's friendly against Madrid and the one against Monaco because the context of these two matches is different even though they are packaged like pre-season matches.
Against Madrid, the context was a friendly match where they tried to test all the players and that was proven by Flick playing almost all the core players and reserve players they had because this was a form of preparation for the upcoming season. In contrast to facing Monaco, although the concept is the same as a pre-season match, the context in this match is the struggle for the Joan Gamper trophy which they made themselves like a competition (because there is a trophy) and seeing from what they dropped in terms of the squad, most of the core players were actually because of the aim to win but they were ultimately slaughtered in the competition they made themselves.
This clearly sets them apart and is a tough job to prepare for the new season because when they faced Monaco it was clear that what they were looking for was a win with the core squad but the opposite happened where they had to lose with a score.