This is old school from coach Diego Maradona. Back in the day we used to call this soccer game 'butts up', where the losing team of whatever kind of game you're playing during soccer practice would have to get in the goal, bend down and stick their butts out. The winning team would take shots at the losers from the top of the box area.
The Argentine players don't hold back either in shooting at their teammates in the video below. Looks like their really firing the soccer ball at their teammates. Really, though, "Butts Up" is actually a fun game to play with your team to get players to relax and have a laugh. Although maybe don't try to nail the ball at your teammates...
But take a look after the winners shoot, the losers get pretty upset and chase the other players down the field - firing the ball at them.
And this is a pre-World Cup practice, it's a bit risky, you don't want anyone to get hurt. Of course, there are more risks playing in games, and this is all in good fun, and good for the team spirit to have some laughs.
There are a lot of people who are expecting Maradona to fail as a coach. Hopefully he gets the last laugh and raises the World Cup trophy for Argentina, this time as a manager.