It's true that the season has just begun, so it's quite natural to see the performance of the big teams has declined a bit... just look at how Barcelona at the beginning of this season was quite difficult to get more points, they were even held to a draw by Rayo, and also Atletico Madrid who is currently in a pretty bad condition, slumped to the bottom of the rankings due to not winning a single match.
These big teams are clearly having trouble organizing their game, but that doesn’t mean this will be the final picture of the season, usually big clubs have the capacity to bounce back and find their rhythm as the competition progresses. So I see these big teams coming back to the top once they get their game together.
Big teams like Barcelona ares such that you cannot count on their poor performance because they are definitely going to bounce back in time and improve their performance, Rayo and Atletico were possibly just lucky and so we cannot count that on Barcelona as been weak and not having been able to start of very smoothly but I believe they are definitely going to do much more better far into the new season and do not be surprise when they end up winning the league title this season.