Mandela, isolated in his 8-by-7-foot cell, was not allowed to play. Instead, he watched until the warden decided to build a wall outside only his window. And once it went up and he could no longer see, he imagined the players out there.
His people hadn't just built and operated a prison soccer league. They had laid the foundations for what was to come several decades later.
That's why Mandela was there on that cold July night at Soccer City. That's why he felt he owed it to his people and to the game that helped keep the struggle alive on Robben Island.
Why, Mandela was asked, did he do an about-face and support sending South Africa's first racially integrated team to the 1992 Barcelona Olympics, though just eight of the 95-person delegation were black? And why did he more famously walk onto the field during the 1995 Rugby World Cup final between South Africa and New Zealand wearing the Springbok national team's green jersey, knowing that among blacks the traditionally all-white team had been a hated symbol of the country's racial oppression?
Mandela's answer always harked back to this: "As I walked out the door toward the gate that would lead to my freedom, I knew if I didn't leave my bitterness and hatred behind, I'd still be in prison."
Sports weren't the only venue where Mandela taught us that apartheid could be a state of mind, not just a system enforced by a regime, and that to truly transcend the damage, both had to change.
But once you know that about him, it's easy to see why he considered himself a lifelong sports fan long after his days as an amateur boxer ended, or why he often said, "Sports has the power to change the world."
Mandela understood sports' power to deliver a message, level societal playing fields, and explode myths of racial superiority/inferiority. One of his most prickly challenges was creating a new South Africa where everyone felt they belonged. He knew the value of sports as a source of pride, an important escape hatch, a ladder out of isolation and deprivation.
Funny as it sounds, other quotes attributed to Mandela over the years -- "A winner is a dreamer who never gives up ... One cannot be prepared for something while secretly believing it will not happen" -- could've just as easily been uttered by Vince Lombardi or John Wooden.
Sports were one of the many areas in South African life where blacks and whites were completely segregated when Mandela walked out of prison on Feb. 11, 1990. The country had been boycotted by a great deal of the world's sports community for decades before he was elected to power in 1994.
But Mandela also knew that sports offer one of those places where integration could be swiftly achieved and held up as concrete proof of what was possible -- both to South Africans and to the rest of the world.