Last month, a trio of the sports biggest stars helped out at the USTA Foundation's "Return Serve Fun Day." Five-time Grand Slam winner Maria Sharapova joined young Americans Ernesto Escobedo and Jared Donaldson to spend some time with the First Break Academy at the StubHub Center.

The annual event aims to expose youths in the Carson, Calif. area to tennis and other athletics.

"That's how it starts. It just starts with a tennis racquet and a tennis ball," Sharapova says. "And you never know where it takes them."