JG's, Juvenile adventure for ages 9-12, by M.D.Marrone

http://www.amazon.com/JGs-M-D-Marrone/dp/1469992728 

When Luke Taylor's deaf little sister is humiliated by a fellow Junior Guard, Jimmy Mack, Luke knows the only way to avenge her is to win what's most important to Jimmy…the Taplin championship.

 

Luke's athletic uncle trains him for the end-of-summer competition by tirelessly coaching him through soft-sand runs and ocean swims.  During the Taylors' family vacation in Yosemite, where Jimmy and his father coincidentally stay, Luke realizes Jimmy's seemingly cool, rich life has been anything but easy.  His broken home and drunken father have produced an embarrassed and pain-filled young man. Game day approaches, and with it comes an unexpected turn of events…  

10-year-old avid reader's review: http://atticusmonthly.wordpress.com/