Time for an underdog winner in La Liga maybe?
Underdog winner, I doubt that!
Last time any small team won League was Leicester City which won the Premier League in 2015-16. But in La Liga, I doubt any team has such caliber. Last season, few teams did beat big teams like Real Betis defeated Barcelona in Camp Nou. We can see such turns this season too. But I doubt any small team can do this consistently and win the league.
Although Real looked poor in pre-season but still Real has players who can turn any game any time. Real may improve significantly in later part of the season.
Whereas, let's not forget about Atletico Madrid. Atletico is strongest team in the league. However, Barcelona has Messi who can beat any team single-handedly. My prediction: either of the Barcelona or Atletico will win the league.