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.
What worse has he done? What's is worse than getting knockout in the biggest competition in club football. The worst you're talking about are just him (the club) having a bad run that he covered up by winning Dortmund to qualify for the quarter finals. This season we already knew there was nothing to fight for in the league and kept our hopes in cup competition which we're out of all we participated in and just left with the champions league so I think him losing against Real Madrid would be very brutal for his career. I miss the old days of Roman Abramovich been incharge, assuming he was still in charge and Graham Potter loses to Real Madrid, he would be given the sack letter immediately.
Nevertheless, I don't think Graham Potter will be sacked (although that's every Chelsea fan wish at this point) and that's because we aren't losing to Real Madrid, the worst we can get is a draw, we'll draw at their home and win in ours. Playing Real Madrid as an underdog is were we'll be having the advantages, they'll be underrating us as usual and we'll surprised them. Don't use our recent bad form to judge this game. This is the champions league and not the premier league. We might be performing badly in the premier league but things get different when we sing that champions league anthem.