Small club or big club, that designation doesn't really depend on the current season and how they are temporarily playing.
Real Madrid is a big club, a huge club and I have a hard time saying that Girona now counts as a big club because after 19 games they are in the second position in La Liga. I think it takes more than that. It takes a lot of things to be considered a big club, but first and foremost titles.
However, it is great that it is not the typical clubs playing for the title at least for the moment. This could change quickly though when Girona has their first losing streak (if they will have one at all, I don't know). Perhaps they keep going like that.
The way Girona played, I am actually surprised that Barcelona is still right under them. Well, that probably doesn't make sense because the other teams didn't play well, teams like Atletico Madrid should have done a lot better compared to what they have done in the past few matches. Barcelona is in the 3rd position but Barca is still 7 points behind and that is something to worry for Barca. By the way, Girona have the same amount of points as Real Madrid. So there is still a chance for them to actually be at the top of the table ahead of Real Madrid. That's how good they are at this season. For a team that got promoted last season, this is a great improvement.
I am actually not surprised at all that Barcelona is still behind Girona. You can pick a single game of course and then see that Girona made some weak plays during a certain game, but when you consider all the games combined, the simple explanation why Girona is ahead of Barcelona is because Girona is playing better than Barcelona in all respects. Girona has the best offense in La Liga by far and in comparison to Barcelona their defense is about the same, only slightly weaker than Barcelona's defense. But this is the problem Barcelona has. Their strikers don't function the way they want them to. That's the reason why Xavi freaked out about Lewandowski and screamed at him that he should finally start to run more. There is a lot of pressure in Barcelona and it isn't getting better.