Japan's former World Boxing Council super bantamweight champion Toshiaki Nishioka announced his retirement Tuesday, a month after losing a world title bout to Nonito Donaire of the Philippines.
"I have done what I should do. I am fully satisfied with my boxing career," the 36-year-old left-hander told a press conference in Tokyo. "I have experienced excitement many times through 18 years as a pro boxer."
Nishioka, nicknamed "Speed King" for his fast-paced fighting style and dreaded for his devastating straight left, made his professional debut in 1994 and became WBC super bantamweight champion in 2008.
After defending his crown for the seventh time with a 3-0 decision over Mexican Rafael Marquez last December in Las Vegas, he was named the so-called "emeritus champion" of the WBC division on March 15, leaving the regular title vacant.
The crown was taken over by Mexico's Abner Mares on April 21 when he beat Puerto Rican Eric Morel in El Paso, Texas, in a title bout.
In a world super bantamweight title unification fight in Carson, California, on October 13, IBF and WBO champion Donaire stopped Nishioka in the ninth round, flooring him twice and handing him his first defeat in eight years.
"I am confident of becoming champion again if I fight boxers other than Donaire," said Nishioka, who is set to open a gym and train young boxers.
"But I cannot think of any better fight than the one I had with him."
The Japanese fighter has a professional record of 39 wins including 24 knockouts, five losses and three draws.
Donaire said in a statement he felt proud to have fought a "speedy and brainy boxer" like Nishioka and sent best wishes for his future.