Chelsea team has been able to perform well in previous matches. There are some players in the Chelsea squad who are currently at their best. However, some matches were very badly defeated by Chelsea. As such, Chelsea are in a fair position.
Chelsea have not shown any improvement in form it's just random they can do it can be very good sometimes but they can be completely poorly in other games. When they face Real Madrid they can win but it's not impossible to lose with a landslide score because Real Madrid is a team that is quite sharp in front and Chelsea have problems defending and actually also upfront, this will be a test for Potter whether he is capable enough make his team go against Real Madrid and win or not, but many fans still doubt Potter's ability to take Chelsea further in the champions league.
As far as Potter is concerned I'm not that sure if Chelsea can perform well against Real Madrid. Real Madrid is well experienced when it comes to champions league and Potter is not very experienced coach in champions league that can be able to tackle team like Real Madrid. Real Madrid have better chances of beating Chelsea, Chelsea has good players but still their performance have not been really productive and won't be good enough to challenge Real Madrid.