Carlo Ancelotti can indeed make some changes or rotation of players to cover the gaps due to the many injured players but it will not be effective, now the situation in the Real Madrid team is very difficult and they must bring in new players in the January transfer market later, otherwise it is likely that Real Madrid will not be able to compete for the title.
He has to make changes with players they have in main squad and from youth academy too. Injury crisis like this will open more opportunities for young players and who know one or some of them will light up their career since this season.
For two months before the transfer market opens, maybe Carlo Ancelotti can still survive with the existing squad as we know that Carlo Ancelotti is a coach with a lot of experience and he should know what he is doing.
Real Madrid will need one or two defenders in the winter transfer season in bought transfers or loan transfers. They have enough good attacking players and can rotate them easily but in defense, they lack of enough players for rotation and with some injuries recently, things are worse for Real Madrid. Getting one or two defenders in the winter transfer season will help them to avoid unwanted situation in hardest months of season, that can decide they win titles or not.