Less than an hour after an undisclosed injury forced former light heavyweight champion Quinton "Rampage" Jackson to withdraw from his Oct. 13 fight against Glover Teixeira, UFC 153 took another major hit.
UFC president Dana White announced the withdrawals Tuesday.
"Rampage is hurt and is out of UFC 153 in (Rio de Janeiro)," White said on Twitter.
"Now, Aldo is out with a foot injury, main and co-main in the same day. Another amazing day at the UFC; we have some work to do."
According to Andre Pederneiras, Aldo's trainer and manager, Aldo has an infection in his right foot and ankle -- it's worse in the ankle, Pederneiras said -- the result of an accident on Sept. 1 in which a car hit the motorcycle he was riding in the Copacabana section of Rio de Janeiro.
At the time, Aldo said the injuries were minor and would not prevent him from defending his title against Edgar.
A leg injury forced Aldo to withdraw from a July 21 bout against Erik Koch at UFC 149 in Calgary, Alberta. The fight was rescheduled for UFC 153.
But Koch would suffer a partially torn medial collateral ligament in his right knee and withdrew from the bout, opening the door for Edgar.
Aldo (21-1) has not fought since Jan. 14 when he knocked out Chad Mendes in the first round at UFC 142 in Rio de Janeiro.
The fight against Teixeira was to be Jackson's last with UFC.
Jackson (32-10) has lost two consecutive fights.
He suffered a knee injury before his most recent fight against Ryan Bader on Feb. 26 in Saitama, Japan. The injury hindered Jackson's training and he was unable to make the 205-pound light heavyweight limit.
It was the first time Jackson failed to make weight in his professional mixed martial arts career.
Jackson and Bader competed at a catch weight of 211 pounds. Bader won the fight by unanimous decision.
Information from ESPN.com MMA reporter Joshua Gross was used in this report.