When an object such as a ball moves you should assess with your eyes where the object is in space. Then a movement follows that involves use of your hand or foot so that you can influence the object. This is a complicated process that children need to practice.
Children should have control of their arms, legs, hands and feet. The body should do what the brain tells it to do.
Now comes estimation. A child learns throwing and catching and kicking. A child learns to use speed and power. Consider the difference between a balloon and a football.
When counting these same skills are being used, one must first get physically master the skill before being able to count mentally. For writing, good hand-eye coordination is also necessary.
-bump into things
-poor at writing from a board to the book
-poor at cutting
-poor in ballgames
-poor at counting resultative
-finding math difficult