The 23-year-old will be sentenced in May.
Southpaw Williams was still a teenager when he won silver at the 2000 Olympics in Sydney, losing 27-20 to Uzbekistan's Mahamat Abdulaev in the final (Abdulaev also outpointed Miguel Cotto in the Games). He then launched what many believed would be a glittering professional career. But a $1.4 million signing on fee made him soft. He struggled to keep his weight down and was well outpointed by Mexican late substitute Juan Valenzuela in a 10-rounder in 2003, after which HBO dropped him.
"He didn't have that much power, just a lot of speed," said Valenzuela.
Worse followed, when Williams was outpointed by 43-year-old Manning Galloway in an eight-rounder in April last year, and he drifted off the scene altogether.
Two other men, one a former leading lightweight amateur, Marshall Martinez of California, were also involved in the conspiracy.
The men posted more than five kilograms of cocaine from California to Williams' home city of Cincinnati. That quantity of cocaine could have a street value of up to $750,000, authorities said.
They used cell phones to coordinate the pick-up in Cincinnati.
