Salzburg and Brest are certainly not equal opponents for Real Madrid in the Champions League, but still these two teams must be taken seriously in the match. Especially Brest, they have been really good over the past 6 matches where they are ranked 7th with 1 loss and 1 draw and 4 wins.
Ancelotti must know what they have to do because their current focus is only to be able to secure full points so that their position is not bad to qualify even though they have to do it through the play-off path.
It is undeniable that these two clubs cannot be underestimated, especially since they must have the same target and desire to qualify (for Brest) and block other clubs from following Slazburg who are likely not to qualify so that in the end Ancelotti cannot underestimate them, especially when competing against Brest because they are really unpredictable at this time in the Champions League.