Yes, Atletico Madrid has great potential to interfere with Real Madrid's chances of defending the title. My prediction this season is that the La Liga title race will be competitive again, even though many people still favor El Real.
It's still too early to say who can compete with Real Madrid in La Liga. Atlético start the last season also not bad, but then even Barcelona, which had a very difficult season, managed to get ahead them. So far, Real Madrid looks like the favorite for me, and in order not to get too far ahead, let's look at Saturday's match against Celta. I think that it will not be a problem for Real Madrid to beat them for odds 1.7, which is not bad at all.
The teams that get used to stay in top will remain there with slight change for the ranking. I assume ATM, Real Madrid and Barcelona will get 3 spot for CL. Sevilla might lose its spot for Villarreal, Betis or Sociedad but it is early to judge according to the current results we see. The transfer window didn't close yet and every team could reinforce its squad including Barca! I can't believe when I read every so on a new name they are trying to sign!