The Chelsea midfielder tore ligaments in his right ankle during his side's 1-0 victory over Portsmouth in the FA Cup final on Saturday.
"There's naturally a lot of disappointment. It's bitter to get a diagnosis like that two or three weeks before the World Cup," Ballack was quoted as saying on Sky Sports.
"But that's football. That happens. Life goes on. He (Germany coach Joachim Loew) is naturally disappointed. I'll fly down there (Sicily) now and we'll let it all sink in."
Ballack helped Germany reach the 2002 World Cup final and the 2006 semi final.
He is an indispensable member of the team's squad but Loew will have to pick a replacement before the start of the World Cup.
"We are shocked, no question about it, and we are all very, very sad," Loew commented.
"He is a very important player for us, a world class player who played a very important role in decisive games for us."
Germany open their campaign against Australia on June 13. They will also face Ghana and Serbia in Group D of the World Cup.