In any peak performance, the athlete is totally oblivious to the outcome and instead is completely absorbed in the here and now of the actual performance. An outcome focus will almost always distract and tighten up the athlete insuring a bad performance. Furthermore focusing on the outcome, which is completely out of the athlete's control will raise his anxiety to a performance inhibiting level. So if you truly want your child to win, help get his focus away from how important the contest is and have them focus on the task at hand. Supportive parents de-emphasize winning and instead stress learning the skills and playing the game.
Comparisons are useless, inaccurate and destructive.
Each child matures differently and the process of comparison ignores significant distorting effects of developmental differences. One may physically have the build and perform like a 16 year old while the other, a late developer, may have the physical size and attribute of a 9 year old. Performance comparisons can prematurely turn off otherwise talented athletes on their sport. The only value of comparisons is in teaching. For your child to do his very best he needs to learn to stay within himself.