Chelsea are two times champions league winners therefore nobody should be saying Chelsea isn't a big team. Not many teams have won more trophies than Chelsea. Just because they were going through some difficult times doesn't mean they're not a big club. An example is Manchester United, they have been awfully recently but still a big team. History can't just be forgotten because it's history that makes clubs big. There are some clubs that are just becoming big recently but the ones that have being doing it for a long time can't be disregarded. Chelsea have a good squad now and I won't be surprised if Chelsea end up winning the champions league.
Anyone who will rate Chelsea as an average or small club probably just started watching football games recently because how will you rate Chelsea as a small club. Chelsea as a football club is 120 years old and in these years they have achieved so much to be rated as an elite club and their reputation speaks volume.
You are right, Chelsea is not a small team and we can see that by there achievement's over the years them winning PSG in the FIFA club world cup competition shows that they are still even very much inform, and right now Chelsea is very much inform and there's a possibility that they can even lift the champions League trophy next season they have young players that are very inform and playing very well so they are good to go next season champions League competition.
Just like you said SatoPrincess that anyone who will rate Chelsea as an average or small club probably just started watching football games recently, because Chelsea football club has really achieved a lot and they have one of the biggest fan base in the world and the reason why they have this much fan base is because of how good they where, so saying Chelsea is an average club just means that you started watching football recently and you didn't bother to even go through the history of football.