Mackey's record-breaking 75-yard touchdown reception carried the Baltimore Colts to a 16-13 Super Bowl win over Dallas in 1971, and it helped propel one of the league's greatest tight ends into the Hall of Fame.
"Mackey was the smartest man in the room," former quarterback Jack Kemp said at his induction ceremony.
But these days, John Mackey is a shadow of the man who had such an impact on football during his ten year career – a career in which he was tackled hundreds of times and sustained a concussion.
Today he still wears his black cowboy hat – once his trademark – atop his six-foot three inch athlete's body, but his mind is not longer as fit.
At age 65, Mackey has dementia.
He showed us his championship rings several times, unaware that he was repeating himself.
We asked his wife, Sylvia, if he can take care of himself.
"It's possible that he could," she said, "but I wouldn't chance it anymore."
Sylvia Mackey doesn't blame head trauma for her husband's condition, and scientists have not established a direct connection. However, a University of North Carolina study into 2,500 former NFL players showed they faced a 37 percent higher risk of Alzheimer's disease than other men their age.
Former players do not qualify for disability from the NLF because they can't prove their injuries are caused by playing football.
Old-timers like Mackey didn't make anywhere near the multimillion dollar salaries of today, so families are struggling to pay for care. Last May, in a letter to then-NFL commissioner Paul Tagliabue, Sylvia pleaded for a financial assistance for former players like her husband.
"We recognize that there are a number of players, and a growing number of players, recognized to be struggling," Harold Henderson, the Executive Vice President of the NFL said.
The league and the NFL Players' Association have responded with the "88 plan" – named after Mackey's number. It provides $88,000-a-year for nursing home care and up to $50,000 annually for adult day care.
Still, there's the nagging question of whether football-induced concussions can lead to illnesses like Alzheimer's and how the league should protect its athletes.
"We have certainly stepped up the research on protective equipment," Henderson said. "We are looking at new rules and procedures to determine if we need a different handling of players who suffer concussions in terms of when they might return to the field."
Sylvia Mackey says she's just grateful for what she has.
"It's disappointing but you can't cry over spilled milk," she said. "You can't go back and wish that something is that can't be, so you have to look at how to make the best of the future."
For Mackey the future is again being part of the fight for his old football colleagues.