It is fundamentally different from last season when Barcelona had by far the best defense in the league. If they now can't solve the problems they have in their defense, this season won't be very successful for them. I am also not convinced of their offense. Yes it is Lewandowski there, but it is not the world soccer player Lewandowski from a few years ago. If they have a defensive performance like that against Real Madrid, they will again be destroyed like in the second game in the Copa del Rey last season.
Overall Barcelona defense is still strengthened by players who looked charming guarding Barcelona defense area last season. Villarreal is a strong club, they also play at their own headquarters, in my opinion it is very natural that Villarreal has the ambition to win matches in front of their supporters.
The three goals scored against Barcelona show how much Villarreal wants to secure full points, but Barcelona are much better than those who managed to score four goals. I don't really focus on Barcelona defense, it's normal for them to concede three goals because Villarreal has a good attack. Barcelona managed to keep a clean sheet in the previous two matches, conceding three goals is not a big problem, but Barcelona players must be able to close the movements of opponents who want to penetrate their defensive area.