The Importance of (Multiple) Sports: Stop Specializing In Sports So Early

Multi-sport participation, by contrast, leads to better performance (because kids get a chance to develop different sets of skills) and greater enjoyment of the game, says Farrey. The headlining athletes at the event echoed the idea that having kids do more than one thing is a plus.

• Ryan McDonagh, captain of the New York Rangers, won a state championship in baseball and was an all-state football player in high school before narrowing his focus to hockey. "Playing other sports was good for my hand-eye coordination and strength," he says. "And it was positive socially, too: I hung out with a bunch of friends who played each sport." He's grateful that his parents never pushed him to pick one, and urges others to take the same tack. "There is so much out there for your kids to explore, and you should let them," he says.

• Laila Ali, former boxer (and daughter of fight legend Muhammad Ali), surprisingly didn't grow up playing sports and was never pressured to do so. She plans to make sure her kids, ages 7 and 4, try a number of athletic pursuits. "It's important for kids to be active, and to teach them to stick with activity, but not push them to get serious unless you see they have real passion for one thing in particular," she says.

• Nastia Liukin, former Olympic Gold Medalist in gymnastics, says she "tried everything"—tennis, running, skiing—as a kid. Her father, Valeri, a former Olympian who coached her to greatness, initially steered her away from gymnastics because he knew how challenging the training regimen was. She chose it anyway but continued to cross-train by playing other sports on her off day. "Expose your kids to different things, and then let them do what they love—not what you love or their coach wants," she says.

For every such story of a champion, though, there must be 1,000 cases in which a child gets seriously injured or gives up a sport for good (and never picks up another activity). That is exactly what Project Play is trying to prevent. The initiative is supported not only by the USTA but also a number of sports leagues and national governing bodies, including the NFL and Major League Baseball. "The idea is to have a variety of athletic experiences to make sure kids have the childhood they deserve," says Farrey. Sounds like a good plan—and a smart move by the USTA, which would love more homegrown U.S. Open champions but is even more concerned with growing the game of tennis.