Tags: tennis, tennis ball, tennis balls, roger federer, novak dokovic, federer, rafael nadal, dokovic, nadal, serena williams, andy murray, maria sharapova, sharapova, john mcenroe, venus williams, andre agassi, caroline wozniacki, pete sampras, ana ivanovic, kei nishikori, nishikori, milos raonic, stan wawrinka, angelique kerber, andy roddick, simona halep, martina navratilova, john isner, bjorn borg, tomas berdyh, juan martin del porto, nick kyrgios, steffi grag, agnieszka radwanska, jo wilfried tsonga, chris evert, eugenie bouchard, billie jean king, lleyton hewitt, samatha stosur, petra kvitova, gael monfils, garbine muguruza, jimmy connors, victoria azarenka, svetlana kuznetsova, david ferrer, ivan lendl, boris becker, dominika cibulkova