In 1974, a sports journalist named Heywood Broun famously said, "...sport doesn’t build character. Character is built pretty much by the time you’re six or seven. Sports reveals character." 
In a recent article in the Journal of Youth and Adolescence , Mr. Broun's ideas have found some solid scientific support. Character does seem to be based on foundations that are built in the early ages and participation in sports seems to bring out the best in children with good character. What Mr. Broun missed in his statement is a linkage between these two ideas; namely, that participation in sports in the early ages can predict positive character traits, which lead to increased motivation to participate in sports, which in turn lead to the development and expression of character. In other words, the ways that children express themselves as they prepare for and engage in sports do reveal character, but the character that is revealed may have a basis in their sports participation.
Participation in sports creates character, builds character, and reveals character.
When children participate in formal or informal sporting activities at early ages, the focus is usually on fun. Most coaches and parents are not expecting a 6-year-old to be very good at soccer. I can tell you from personal experience that a soccer game among 6-year-olds is not exciting. But it is cute. The players look incongruent in their uniforms, and the soccer ball that they're kicking in errant directions is bigger than their heads.
In most cases, these opportunities that children have to play on a team at an early age are saturated with praise from parents on the sidelines, and kind feedback from coaches, who are volunteers with no "skin in the game." These are not cut-throat matches, and everyone gets a chance to play. In some cases, no one even keeps score.
Most 6-year-olds on a team are at similar heights, weights, and levels of ability. Attempts are made to create a low-risk environment for each child to try out different positions, strategies and methods of playing. There is positive reinforcement given for trying, not just succeeding, with a lot of value placed on "doing your best."
In the field of education, this kind of learning environment is called scaffolding. Scaffolding happens when you take a child at her current level of ability, and then you guide her through the effort of attempting something that is just above that level. With scaffolding, coaches, educators, and parents are looking to increase the chances that a child will succeed, but also want the success that she achieves to feel like an actual accomplishment.
If your child already knows how to add 2+2, you can give him a math problem that asks him to add 2 and 2 together. He will succeed in getting the answer, but he will not likely feel a tremendous sense of accomplishment. If, however, you see that your child has mastered the addition of single digits, you can guide him toward understanding how adding a single digit number to a double digit number is only slightly more complicated than what he already knows. When he successfully answers the problem 21+4, he can feel proud of himself.
The pride that your child can have when she solves a math problem that requires a new set of skills is psychologically similar to the pride she can feel when she learns how to kick the soccer ball with the side of her foot, or pass the ball between two cones. A good coach will start with cones that are wide enough for everyone to be able to kick a ball between, and then gradually make the spacing between the cones narrower.
The research from the Journal of Youth and Adolescence that was cited above suggests that these early experiences are "critical for the development of preliminary motivational beliefs." Now, what are those? Motivational beliefs rest on a belief in self-competence. When a child believes that she can accomplish the task at hand, even if it is slightly challenging, she is motivated to try hard to succeed. This research I am summarizing here points to a very interesting circular pattern; namely, early participation in sports is related to perceptions of self-competence, which is related to higher levels of motivation, which is in turn related to a greater desire to continue participating.
This pattern seems to work in almost any area of life. If you try something, and find that you are good at it, you are more motivated to try to get better. As you get even better, your interest in and liking of the activity will increase. Competence is a foundational need. The more opportunities you have to play in a low risk environment, where winning is less important than fun, exercise and social contact, the more likely you are to continue participating. As a consequence, you are bound to get better.
In a time where child obesity rates are disturbingly high, providing your child with early level physical activity is a great gift you can give, which can very well lead to a lifetime of health, physical activity, social competence, and well-being. Take your child outside and get him moving around. While you're at it, move around with her. There's no lower risk environment than playing with your child, and the benefits to both of you are outstanding.
 1974 May 2, The Salina Journal, Heywood Hale Broun will speak at KW, Quote Page 12, Column 2, Salina, Kansas. (Newspapers_com)
 Dawes, N. P., Vest, A., & Simpkins, S. (2014). Youth participation in organized and informal sports activities across childhood and adolescence: Exploring the relationships of motivational beliefs, developmental stage and gender. Journal of youth and adolescence, 43(8), 1374-1388.