You're right, Atletico Madrid is a dangerous club. I think they are a dangerous because of the irregularity of their performance. Often they surprise everyone with their good performance. However, we expect good performances from renowned clubs like them.
Now there is no chance to think Barcelona club is weak. Xavi is experienced enough. He is trying to bring back the good days of Barcelona. So now the match between Atletico Madrid vs Barcelona will be competitive. However, in this match I would expect the match to be a draw. Xavi does not want to lose points.
both teams are evenly matched, so betting for a draw is not something wrong. but maybe Atletico can beat Barca with a few goals.