What's the Barcelona six second rule? No, this isn't like the three second rule, where you can still eat something off the ground if you pick it up quick enough. But yet, in a way, it is, because it's all about reacting quickly on the soccer field and winning the ball right away.
After Barcelona loses possession of the ball, which they don't do often, the whole team fights to win the ball back in six seconds. Once they lose the soccer ball they don't drop back or concede space to the other team. No, they all press towards ball and try to win the ball back as soon as possible.
Related to this, is one of their secrets to success - pressing the ball when any member of the opposing team turns their back with the ball. Watch how even Messi fights to win the ball back in the attacking third, if he actually loses the ball, rather than letting the other team move up the field and towards Barcelona's goal.
The key though to Barcelona's pressing defense is working as a team, everyone ready to react and try to win the ball. The pressing is immediate and unrelenting. Nobody gives up. Everyone fights for each other. It's also about reading the play and predicting where the other team will try to play the ball.
So while Barcelona does press and crowd the other team when their trying to bring the ball out, it's about the players just behind the pressing players who need to read the play and win the ball or intercept it. You often see Sergio Busquets, Rakitic, and Pique win balls as the other team trys to send a longer ball to escape pressure.