Well, Real Madrid has the opportunity to get into 8th place if they win the match against Brest today. But Brest doesn't seem like an opponent that will be easy to beat. Moreover, in today's match Brest is also the host. I even tend to think of a draw for this match. But Real Madrid will probably fight harder because this is a good opportunity for Real Madrid which could even have a chance of not having to go through the play-offs. As long as one of the teams currently ranked in the top 8 loses points in today's match.
Brest in Ligue 1 is actually going through a difficult time. Because they are currently only ranked 8th. In contrast to Real Madrid, which is currently at the top of the Laliga standings, so favoring Real Madrid seems to make the most sense for this match.
Real Madrid can beat Brest or any opponent in Champions League where they're King in history. They are strong in this season and problems in early of season, don't turn Real Madrid to a weak team there. In this very important match, Real Madrid can win it, even their oppponent is stronger than Brest. However Real Madrid no longer have control on their rank in top 8, they can beat Brest but they will have wait for bad results from other clubs for getting in top 8. It requires many conditions converge at the same time so I assume Real Madrid will have to play playoff matches as a seeded team.
It's a cost they have to pay after several bad matches in early of this season. They came back strong but it's kind of late for them to get in top 8 and avoid playoff matches.
That Real Madrid are king of UEFA Champions league as you said doesn't mean they can't be defeated by any other team that's very wrong as long as football is concerned nothing is impossible don't even be surprised if they lost to Brest tonight just see it as football very unpredictable, but I doubt if they will take this game for granted knowing that winning in this will be very important for them considering the position they are in their group, Real Madrid has improved in form in their past game so I believe that Real Madrid couch Carlos Ancelotti will do everything possible to win against Brest tonight in their UEFA Champions league game to stand a chance of qualifying to the next face of the league.