It’s a familiar ritual: Ahead of a serve, a tennis player will be brought two, three, or even four balls by a waiting ball boy or ball girl. One by one, the player will test out each ball—perhaps by bouncing it off the floor or on the racket, or cupping it in their hands. Any balls found wanting will be chucked away, while the ones deemed acceptable are duly thrown into the air and walloped across the net.
But what’s the difference between the balls that make the cut and those that don’t? And why do male players seem so much pickier than female players when it comes to tennis ball preferences?
Most tennis balls are much the same. On the inside: a rubber core, containing pressurized air. On the outside: a fuzzy green-yellow felt shell. At the US Open, however, the balls played by men and women are subtly different. Men use Wilson’s extra-duty version, with a black Wilson logo and a red US Open print. Due to Women’s Tennis Association regulations, women use different balls—regular-duty, with the colors reversed. They’re both the same size—Type 2—but the regular-duty balls are a little sleeker, with shorter fibers, and play a little faster by consequence.
There’s the rub. Because of the longer fibers, extra-duty balls have greater potential to be bashed around in use, making the fuzzy felt even fluffier. To minimize perceived drag as the ball soars over the net, male players generally prefer tennis balls to be as unfluffed as possible and will select accordingly, however slight the difference. For female players, there’s less variation, hence less need to pick and choose.
That’s why, when the Swiss player Roger Federer serves, he’ll look for the “fastest ball for the first serve,” he said in 2009. “I don’t always do it. Depends when the balls get used and the rallies are long, obviously some balls really fluff up.”
But not all players are as systematic. French player Jo-Wilfried Tsonga, who may knock back as many as 60% of the balls he’s offered, dismissed it as little more than ritual: “I think this one is good, I think this one is good,” he said, jokingly. “They’re all the same.”