Real Madrid has 1 key player who gets injured (Courtois). He is expected to return on October 15.
Barcelona has 3 center backs injured, but Kounde seems to be available before the El Classico.
Kessie is also expected to return on October 14.
If all expected players are available before the El Classico match, both teams will have complete key players in their lineups. So, I think both Real Madrid and Barcelona will be well prepared.
Regarding their current performances, I think both Real Madrid and Barcelona look convincing, they are in a good shape. Although Barcelona was just defeated by Inter Milan, I don't think it will bring a big impact on El Classico result. El Classio match is always unpredictable, even Real Madrid is a superior team, it won't guarantee to win. Don't forget that Real Madrid experienced many times lose at home.
Please check:-
https://www.transfermarkt.com/real-madrid/kader/verein/418-
https://www.transfermarkt.com/fc-barcelona/kader/verein/131In this case Courtois, Kounde and De Jong will most likely play and even Ancelotti himself has said that Courtois will be fit and can play ahead of El Clasico but for Barcelona their defense is still missing Araujo there.
On the other hand, in this El Clasico, it will be in Madrid which is likely to be filled with Madridistas who can become the 12th player from Madrid which makes this of course very exciting to watch whether Barcelona is indeed able to face Madrid and increase the Margin points or will be overtaken again.