Mundine was to have fought Kessler at the Entertainment Center in Sydney, Australia, on May 11. But the champion hurt his back while training in Denmark.
Mundine's manager, Khoder Nasser, said he had been told Kessler would be sidelined from four to six weeks after the scheduled bout. Nasser said it was too soon for him to know whether Mundine would schedule an alternate bout while waiting for Kessler to recover.
The 29-year-old Mundine has an overall record of 23 wins, with 18 knockouts, and two losses.
Some information for this report provided by AP and AFP.