The Super Six light heavyweight tournament that was to be held at Emperors Palace near Kempton Park on August 9 has been cancelled.
Rodney Berman's Golden Gloves Promotions will, instead, now present a card in which Thabo Sonjica will defend his IBO super-bantamweight title against Roli Gasca from the Philippines.
The main reason for calling off the Super Six tournament was the looming withdrawal of former IBO super middleweight champion Tommy Oosthuizen.
Oosthuizen would have returned to the ring after an absence of almost a year and his fight would have been the main drawcard. He was scheduled to make his debut in the light-heavyweight division.
Berman said on Sunday it was up to Oosthuizen, who is undefeated after 24 fights, to "turn a corner".
Oosthuizen has experienced problems and was not at his best in his recent bouts. Berman said the talented fighter would have to show he is ready to do justice to his ability.
Other boxers who were to have fought in the tournament included Johnny Muller, Rayno Liebenberg, who is rated No 6 by the WBC, Roberto Bolonti from Argentina, Russian WBC No 12 Denis Grachev and Namibian Wilbeforce Shihepo.
Liebenberg and Grachev will still take part on the replacement card.
Speaking about the new card, Berman said: "Sonjica has emerged as one of South Africa's most exciting boxers. While fighting mainly in the Eastern Cape he has won the IBO title."
Sonjica knocked out Toto Helebe in 2 minutes 36 seconds a month ago to retain his IBO super-bantamweight title.
Making the first defence of his belt, Sonjica beat Helebe, the SA bantamweight champion, in the main fight of a tournament at the Orient Theatre in East London.