Nery scored a fourth round technical knockout in their Aug. 15 Tokyo bout but the Mexican, who has a 24-0 record including 18 knockouts, is under investigation by the WBC after an out-of-competition sample tested positive for a banned substance.
"There is no way (for Yamanaka to continue his career) unless a rematch is called. The fight means that much," Yamanaka's Teiken Gym president Akihiko Honda was quoted as saying by the Kyodo News.
Yamanaka, who has a 27-1-2 record including 19 knockouts, would not fight another opponent for the belt even if Nery was stripped of the title, Honda said, adding he expected to hear the WBC's findings in the next two to three weeks.
The 34-year-old Yamanaka made 12 successful defences of his title until he lost it to Nery.
(Reporting by Amlan Chakraborty in New Delhi; Editing by John O'Brien)
