It all depends on the available players. When Barcelona had its best times, they had like 15 top players and almost didn't matter whether one or the other played. Of course some can't be replaced, but still that's what it is important. How many players are injured? Who is in top condition? It's all about that. Imagine Lewandowksi or Kane would be injured. Both teams had some problems to replace their central striker, which is quite normal. But if the coach sees that everyone is on a top level mentally and physically, he will surely pick the best eleven players for both games. It#<s not the time yet to take too many actions in terms of rotation if it is not necessary or if the player is not super young and unexperienced.
At this period Barcelona would just be hopeful that the players can handle the both matches. I have thought of team rotation and I will say both matches are seriously important at this stage. Barcelona have already lost a champions league match already and another loss to Bayern Munich will mean they have just one more game to lose to miss out on the direct qualification. For the Laliga match they have lost one and it basically when he wanted to do a rotation which shows that Barcelona doesn’t have that squad to do heavy rotation now.
If they decide to do it against Real Madrid even if Madrid wins they will still remain on the top with a point but that will be a moral boost to Real Madrid if they win the el classico and would be a pressure on Barcelona. Let Hansi click just stick to his formation and hopefully they don’t get injured