At the beginning of a match day (countdown in the squad screen) your team must be complete (7 players). You will be deducted 10 points for each position that is not filled.
In addition, points can be deducted if you collect minus points with all your players on a match day.
You will not receive any points for the performance of your players if your account balance is negative at the beginning of the match day (at the end of the countdown).