IMO, not only in defense but also in midfield after Kroos retired, while Modric's performance is not like when he was still in his prime.
-snip
For me the midfield is not worrying because there is still Bellingham who is ready to replace Kroos and the player's performance is also very good and can contribute perfectly. And regarding Modric, I agree that he is no longer like his glory days because age greatly affects his physical performance. However, whatever your concerns about Madrid midfield, it is actually not the main problem but the defense line that Ancelotti must prioritize. So in the next match Ancelotti only needs to stay focused on finding ways to strengthen Madrid defense and maintain the strategy in the attack line. In this way a draw or win is a definite result.
The main reason why Real Madrid still keep Modric is to maintain the depth of the game and than maintaining the transition in midfield. The impact of Kroos departure is very much felt, it is difficult to find a midfielder of his caliber, and I think Modric role is more than just a rotation option in Ancelotti game plan. This is most likely his last season at the club, and due to age, we may see the Croatian retire next season, following in the footsteps of Kroos.
Real Madrid decline in performance is not due to a lack of balance in midfield, but purely due to injuries. Ancelotti has had a hard time experimenting with determining his starting XI, because the rotation options he has are decreasing with the increasing number of injured players. If all the players are available, Real Madrid will be able to perform according to expectations, and can even help Mbappe adapt quickly in the front line. However, I personally think Ancelotti can lead his team to full points in the next match against Atalanta and secure their chances of qualifying for the last 16.