It is clear that Ancelotti will find a player on the bench who can replace the injured one, but does Real have a player of Carvajal's level on their bench? This is a rhetorical question, there is no such player, but they will just have to learn to play without him because he is out due to injury for a whole year. El Clasico is always a special game, and this confrontation is always unpredictable, every season due to different circumstances one of the teams can be stronger and despite Real's losses, I am ready to say that Barcelona can beat Real.
I am very confident that Carlo Ancelotti will be able to find a solution, perhaps even changing strategy and formations
After all, you may have noticde how he is a strategist on the football pitch and Real Madrid have in fact won a lot with him while spending relatively little, just see past years
But there is always a possibility that he will fail this season even though he has tried various strategies. I admit that Ancelotti is a great coach who has won many titles with the teams he has coached, but his strategies will not always be effective every season. Competitors will find a way to stop them on the field and Real Madrid will have a hard time winning matches. That is the goal of every team, to win matches or try to make it difficult for the opponent to win matches.
Without some of his best players Ancelotti can probably win games, but he can't win them all without the players he needs. Sometimes one or two players can change the game and bring the team an advantage, while when they are absent for whatever reason, the team will struggle to win games.