India, Sept. 4 -- On a green-tinged US Open court, like they were a couple of decades ago, a youngster sporting red shorts and sneakers leaps over the service line - both feet close to each other, the right arm and racquet cocked behind the head while the left arm flows loose - and smashes a high ball across the net. Like a slam dunk in basketball.

On the shining blue of the Louis Armstrong court under lights, like they are now for night sessions, a 40-year-old wearing fluorescent green shorts waits behind the baseline for the looping forehand, takes off to meet the ball mid-air with both feet wide apart, and unleashes a crosscourt forehand winner. Like a split in dance.

This is the same guy, 20 years apart, playing elite professional s...