I think for Potter champions league is the last chance to prove himself otherwise he can get fired just after losing the game against Real Madrid, that's why I expect to see Chelsea playing with full power against Real Madrid but on the other hand, since for Real Madrid champions league is the first priority I don't think if Ancelotti will let Chelsea win this game easily.
Graham Potter will not be fired if his team loses to Real Madrid in the Champions League. He has done worse in the past and been given more time and grace to improve the team and overcome their mistakes and difficulties. Even if he loses to Real Madrid, I don't see him being fired; perhaps he'll have to wait until the end of the season for the team to decide his fate with them. Let's just say that this will be a tough match between these two teams in the Champions League.