No wobble should be seen. Try to have a referee approved ball that can be used if the game ball is damaged or lost. Use only safe soccer balls. Some balls become hard or heavy in cold and rain, respectively. The Number of Players Each team should start with 11 players, with one of those being a goal keeper.
Substitutes remain on the bench until requested to enter the field by the coach.
The player has to be waved on by the referee. The AR's signal for substitution is a raised flag with the flag stretched with the other hand. Realization that there are too many or too few players on the field. With too few, get the player to the half line, get the attention of the AR, and explain that there are not enough players on the field. The ref should allow the player to enter.