The Adidas Jabulani, named after the Zulu word for "rejoice," has been by far the most-hated in a continuing series of controversial Adidas World Cup balls. Reinventing the wheel (or sphere, rather), the Jabulani flies further and more erratically than a traditional soccer ball by getting rid of seams and using thermally-bonded panels instead. These alterations, made ostensibly to improve the game, have actually disoriented and hurt both outfielders and goalkeepers. So now the legitimacy of this World Cup, and we're no longer sure if any given mistake is due to the players on-field or the brand new ball they're coping with.
Naturally, when measures are taken to create a different kind of ball for a single tournament, players will complain. They don't need one more thing to worry about on the biggest stage of all. Yet FIFA has specifically asked for special Adidas ball designs that will encourage offense for several World Cups in a row now. Goalkeepers complained in 2002 and 2006, claiming that the increasingly lighter ball would allow strikers to score from unprecedented distances. Beginning with the seamless Teamgeist ball in 2006, goalies also said the ball tended to knuckle, creating yet more difficulty for them. The lack of seams also make gripping the ball more difficult, perhaps resulting in the famous Robert Green bobble that scored the USA's lone goal against England in one of the first games this year.
With this World Cup, "improvements" to the ball have been so extreme that they actually seemed to go against their own purpose. As Spanish goalkeeper Iker Casillas said, "it’s a little sad in a competition as big as the World Cup to have such a poor ball. It’s not just the goalkeepers complaining, but the outfield players as well."
Clearly, the ball has made crosses and longer free kicks much more difficult to perform, as the ball seems to take off and sail over its target whenever it gets a chance. Even Landon Donovan admitted that "you’re seeing a lot of missed chances, a lot of crosses that are mistimed or misplayed that would normally be goals, that are not going in." The ball's light weight and seemingly random knuckling has ruined every team's aerial attack abilities.