"I am very disappointed," Sylvester said. "All of a sudden I felt sick and exhausted. I went straight to the doctor who told me that I could not fight on Saturday. That is a major disappointment for me as I was really looking forward to fighting in front of my home fans in Neubrandenburg."
A representative for Sauerland Event said the fight would be rescheduled "as soon as possible."
"We have to wait and see how quickly Sebastian recovers and then speak to the IBF to set a new date," said Team Sauerland General Manager Chris Meyer. "We are trying to sort this out as soon as we can."
The postponement means Philadelphia-based IBF cruiserweight champion Steve Cunningham's title defense against Enad Licinia (19-2) will also be delayed. Cunningham (23-2) has not fought since last June, when he stopped Troy Ross in the fifth round to win the vacant IBF belt.