Man, looking at the table it's possible for another El Classico this season, if Barcelona and Real Madrid do make it to the semi final or final depending on grouping, but to be honest the numbers of potential El Classico are quite a lot this and it's getting exciting again with the likes of Raphinha, Yamal, Lewandowski, Vinicius Junior, Mbappe, Rodrygo and Jude Bellingham giving good performance in most games. I would really want to see another El Classico in the Champions League this season, though Barcelona has find it easy to trash Real Madrid twice now.
Too early to call this. We are now getting into the no nonsense part of the tournament! I think both teams have a long way to go before they meet. Barcelona may have been impressive in the domestic league and the Supercopa de España against RM, but never underwrite Real Madrid in the Champions' league (this is an unwritten rule

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This is true and that's why I want to see one happen in the Champions League, I know their fans will be hoping or speaking highly before such game about trashing Real Madrid again but in such game I doubt that would happen, the Galaticos will put them in their place.
Also, I think Barcelona are still relatively doing well in their champions league matches till now and somehow I won't be really shocked to see them get there but like you said, it's the Champions League knockout stages, any mistakes or poor performance can likely knock them out.
It is very difficult to predict because the journey in the Champions League knockout round is quite difficult considering that several other teams have almost equal strength, especially Barcelona, who have not proven to show good performance and are also consistent in the Champions League match, regardless of what happens in the group stage, but in the knockout round everything will be different.
Even if it happens, I will really favor Real Madrid, the Real Madrid team has a different mentality in the Champion League competition so several previous matches that occurred in the domestic league between Real Madrid and Barcelona cannot be used as a reference if the two meet in the Champion League match.