The following is from an article on Sherdog.com:
Instead of replacing Shinya Aoki in the Dream lightweight grand prix, the promotion announced Monday that Aoki's quarterfinal bout against Katsuhiko Nagata, scheduled for May 11, has been postponed until June 15.
The delay is due to the numerous injuries Aoki sustained in his two recent bouts against Gesias Calvancante. According to Aoki's family doctor, the 24-year-old grappling prodigy suffered a concussion of the cervical vertebra in his March 15 meeting with the Brazilian and picked up a severely bruised rib in the second battle on April 29.
“Because of the seriousness of his injuries, I have recommended Aoki not to fight again in the next 40 days,” the doctor said. “He has torn some cartilage in his costal area, which prevents him from breathing properly. Aoki has to take two weeks off to fully heal up and as a result cannot compete on May 11.”