Per Manley's daughter, Dalis, the 62-year-old began receiving oxygen because of breathing issues two weeks after testing positive.
Manley, a two-time Super Bowl champion, was named a First Team All-Pro for the 1986 NFL season. He had 18.5 sacks en route to leading the 'Skins to the NFC Championship Game.
Fifteen years after his career ended, Manley underwent a successful 10.5-hour surgery to remove an enlarged colloid cyst on his brain, per ESPN's Tom Friend.
Manley credits the cyst removal with curing his addiction to cocaine, per Sarah Kogod of SB Nation:
"A scan taken at the hospital showed that the cyst had grown to the size of a quarter. He was taken to Georgetown Hospital where he underwent brain surgery to remove most of the cyst. A second surgery months later completed the process.
"When the cyst disappeared, so did all of Manley's urges. He has remained sober ever since, and says he doesn't struggle with temptation. Multiple doctors have told him that the cyst was located in the part of the brain associated with impulse control. His therapist believes that the cyst itself was the root of his addiction."
Manley, who retired from the NFL after failing his fourth drug test in 1991, overcame that addiction and also learned how to read while in the league.
Per Kogod, Manley was illiterate during his career at Oklahoma State but worked up from a second-grade reading level to a 10th-grade reading level after taking some classes and tutoring sessions late during his NFL stint.
Overall, Manley has overcome a significant amount of obstacles in his life, as Kogod noted in her 2015 piece: "Twenty-four years of drug addiction, 38 visits to various rehab facilities, homelessness, four arrests and years of jail time defined him for so long."
Manley, who was a fifth-round pick in 1981, earned the nickname "The Secretary of Defense" during his time in D.C. He is a member of the team's Ring of Fame.