It's hard for me to believe that there is a team in La Liga right now that can beat Barcelona. I don't want to say that Real is a weak team or that they have become worse or weaker with Alonso, but objectively it seems to me that they haven't gotten rid of their long-standing problems in defense yet and in addition they have weaknesses in the midfield, and given this it will be difficult for them to compete with Barcelona, which in addition to a well-equipped and well-played team has a bench that is capable of fully replacing the main players.
You forgot that you are talking about football where surprises happen. Barcelona is in the best form and have one of the best players in the La Liga but that does not mean they cannot be shocked by the least expected team. When they play Celta Vigo, Athletic Bilbao and Valencia and triumph, then we can say no one will beat them because every season, those are the teams that gives them headache, not even the big boys like Real Madrid and Athletico Madrid. The season is just too young to begin to jump into conclusions.
Well, it is too early to specify the winner of la Liga. Anything can happen because it a football game full of surprises and entertainment, But when it comes to Champions League match starts rest of the teams got tired due to busy schedules and at that's why many teams lose their energy and that has a big impact on the performance of the team. For many years, Real Madrid was the only team that pursues the Champions League matches quite aggressively and also wins most as well as leagues, but other clubs such as Barcelona can't even play dominantly throughout the Champions League and got knocked out quite easy by minor clubs every season.
Now if Barcelona remain the strong in the Champions League and they emphasis on UCL at that time then thier is high possiblity that they can show much weakness in the leagues and that will be a vital chance for Real Madrid. Honestly Playing two hard competition in parallel time is quite difficult task for anyone to manage.