Frankly, I also didn't think that Barcelona would only get 1 point in this match because their squad is much more promising than Rayo Vallecano, and Barcelona also has a good record when facing Vallecano. But in football, surprises often occur, and that is what happened when Vallecano surprisingly managed to hold Barcelona to a draw. Barcelona's rhythm looks quite monotonous and they failed to dominate the game, and they didn't even have more shots on target than Vallecano.
This is where the unpredictability in betting lies, there are matches like Barcelona vs Rayo Vallecano, when almost no one doubted that Barcelona should win, but instead there was a draw, which spoiled the bets of many players. It is difficult to say what was the reason for this draw, Rayo defended well and were able to equalize at the end of the match, and Barcelona could not score again, this happens sometimes. I think that this is an exception to the rule, and in La Liga, few will be able to take points from Barcelona.
Actually Barcelona dominated the game when the first half began. And several times they created chances through Rapinha and Lamine Yamal, although they did not really threaten Rayo Vallecano's goal. Until the 40th minute Barcelona finally got a chance to score through a penalty kick. And Luckily Yamal managed to convert it, bringing the score to 0-1 against Rayo Vallecano. In the second half, Rayo Vallecano seemed to dominate the game. They threatened Barcelona's defense and even their keeper several times through Pedro Diaz, Alvaro Garcia, and Andrei Ratiu. In the end, Rayo Vallecano managed to hold Barcelona to a 1-1 draw through a goal from Fran Perez. The score remained until the end of the match. So I think Rayo Vallecano successfully read Barcelona's movements or even their tactics in the first half. This allowed them to dominate the second half with high intensity and equalize the score. Rayo Vallecano even scored another goal. But unfortunately, it was disallowed due to an offside by one of their players.