Pienaar recalled the moment when Mandela walked onto the Ellis Park field ahead of the Springboks' final at the Rugby World Cup, wearing a replica of Pienaar's number six jersey.
"On the 24th of June last month I became very emotional because that morning I got word that Madiba's health deteriorated, and that was 18 years ago that Madiba walked out on the green grass of Ellis Park Stadium in front of 65 000 people," Pienaar said.
"Later that afternoon for the first time in the history of this country people in the cities, in the towns, in the villages gushed out onto the streets of South Africa in celebration.
"It was the first time that we became world champions, which was an incredible moment."
Pienaar was speaking at the Nelson Mandela Foundation in Houghton, Johannesburg this week, where ministers and members of the sporting fraternity delivered a pledge and messages of support for Mandela.
"We would not have had that if it was not for Nelson Rolihlahla Mandela that asked everyone in this country to support the Springboks and embrace them as our team with the slogan 'one team, one nation'," he said.
"Madiba said profound words: 'Sport has the power to change the world and it has the power to unite people in a way that little else does'.
"Sport can awaken hope where there previously was despair, and if we look at our young democracy and what sport has done for our nation, it's been incredible," Pienaar said.
"But you have to have a leader with the vision of Nelson Mandela, and I am very blessed to have shared a platform with him."
Pienaar said he was left with the eternal memory of Mandela presenting him with the William Web Ellis trophy. The statesman punched the air as the Springbok captain raised the trophy.
"I will never forget that beautiful smile on that day and his hands in the air when we won," he said.
The country will once again be asked to unite for a sporting event following the launch of Nelson Mandela Sports Day, which the sport and recreation department announced earlier on Thursday.
The event will see the Springboks and Bafana Bafana playing against Argentina and Burkina Faso respectively at the FNB Stadium on August 17.
On February 3 1996, Mandela appeared in a replica of Bafana captain Neil Tovey's number nine jersey at FNB Stadium. The national soccer team went on to beat Tunisia 2-0 and claim the 1996 Africa Cup of Nations title.
Tovey paid homage to Mandela.
"When I was playing club football that was all we could aspire to and then suddenly the doors to international sport were open to us," Tovey said.
"Madiba has created that environment for us to perform and to put South Africa on the international map."
Tovey said the sports day was an example of what South Africans were capable of doing when they united behind a cause.
"It will be a huge occasion and it is typical of what South Africa is about. We are able to do the impossible in celebration of Madiba."
Pienaar believed the initiative could become one of the biggest sporting events in the world.
"Again South Africa, we are the first. It will be the first time that soccer and rugby will share the same arena in front of this nation," Pienaar said.
"We will share cultural events, and in time can you imagine what this event can become in saying thank you Madiba?" – Sapa