Back passing in the game of futsal is different than that of normal football. Unlike football, back passing in futsal is actually allowed but it does have some constraints. Hence, to clear the air, this is what is allowed and the goalkeeper plays an important role in all this. The same rule applies in futsal as that of football, if the goalkeeper touches the ball with his hands after passing it to his defender, a indirect free kick is awarded. He is also not allowed to touch the ball with his hands when it comes from a kick-in after the ball goes out of play.
On top of that, the goalkeeper is not allowed to hold the ball using any part of his body for more than 4 seconds. He is also not allowed to touch the ball using any of his body parts after he passes the ball out and has not left his half of the pitch or touched by the opponent. The keeper cannot touch the ball in his half for more than 4 seconds regardless of which part of his body is in possession of the ball. If the ball is passed to him by his teammate, the 4 second rule starts.
