Anderson Silva will replace Jon Jones in a light heavyweight bout against Daniel Cormier at UFC 200.
The UFC announced the late replacement for Jones on Thursday, less than 48 hours before the mixed martial arts promotion's biggest show of the summer.
Silva (33-7) is one of the greatest fighters in the sport's history, reigning as the middleweight champion for nearly seven years.
But the 41-year-old has not earned a victory in four fights since October 2012, enduring injuries and a doping suspension that invalidated his only win in that stretch.
Silva, who had surgery to remove his gall bladder just seven weeks ago, will step in against Cormier, the UFC's vaunted 205-pound champion.
Cormier's rematch with Jones was cancelled on Wednesday after Jones was found to have failed a doping test.
Jones has since denied knowingly taking performance-enhancing drugs after testing positive for an unspecified banned substance in an out-of-competition sample taken on June 16 by USADA, which administers the promotion's anti-drug policy.