Everyone is tipping Real Madrid to the quarter-finals of the Champions League. But it would not be right to underestimate the Chelsea team. Because the Champions League platform is completely different. Chelsea reached the quarter-finals on their merits. So it is not right to underestimate any team.
I wonder what you see as "completely different" in the Champions League and in the round robin? The only real difference is that the favorites have bad days and the underdogs have good days and if in a round robin it doesn't matter then in a knockout it can decide the outcome of a certain round. There are no differences in the quality of the game and in everything else. Or are you saying that Chelsea plays special football in the Champions League? I didn't see it - on average they are bad both there and there.