If you end up in the middle in this Barcelona warm up drill you might be there for a while. It's even hard to keep track of all the passes they rack up while the two are in the middle. Sometimes they refer to the game as "piggy in the middle". You don't want to be the piggy.
I wonder if Barcelona plays it with the rule that if you get nutmegged you stay in for another round?
Watch how they play two or three short passes and then ping the ball across the circle to open up the game again - splitting the defenders sometimes. Yes, their tiki taka skills are on display even in this simple warm up drill. I'm guessing they could play this for hours on end and not get bored just don't end up in the middle though, unless you want to work on your fitness.