Some parents won't buy their kid a guitar unless the child takes piano lessons. There's a sports analogy from this article by Terez Paylor of the Kansas City Star:
By the time Evan reached the seventh grade, however, Royce and Teresa found they could deny him no longer, and they let him join a youth football league in Lee’s Summit with coaches who focused on the fundamentals.
It didn’t take long for Royce and Teresa to see that they’d made the best possible decision for their son. Evan was a natural lineman — bigger than his peers, but with advanced agility and coordination developed through playing soccer. Youth wrestling had also taught him the importance of leverage and hand usage.
My boys both want to play football and I've tried to teach them a few things - keep your eye on the ball, catch the ball with your hands out front of your body, get your butt into your tackles, etc. One played soccer for year in '08, but hasn't shown any interest since. Neither wrestle. Both play baseball, but I'm not sure how baseball skills translate to football.