You can't play tennis without tennis balls. Yet an increasingly vocal group of players says that the tennis balls used on tour are behind a major problem: They're causing injuries.

Yellow felt and a rubber core. A tennis ball seems so simple. But reality is more complicated, at least on the pro tours where manufacturers can make balls that fit into a range of specifications ...

The U.S. Open is now in full swing, and nearly 100,000 new tennis balls will be used. Unfortunately, that means thousands of tennis balls will soon be useless to the tournament’s top players.

Keep your eye on the ball. That’s the mantra for tennis players, from beginners to whoever lands in the finals at this year’s United States Open. But each ball will be seen only briefly ...