The bustling centre-forward scored two goals in Brazil's Confederations Cup triumph over Spain in 2013 but was also present as Brazil were hammered 7-1 by Germany in the main event 12 months later.
The 3-0 win over Spain was taken as evidence that Brazil would be firm favourites for a World Cup held in their home nation but Fred looked back with anguish and warned Sunday's finalists not to get too confident.
"The Confederations Cup and the World Cup are very different tournaments, even though both feature top class sides," he told Reuters in an interview via email. "I don't think there are limits to how a team can grow."
"No one expected that result in the World Cup," he added, referring to unforgettable 7-1 defeat. "We played really well at the Confederations Cup and the group was all set, the fans put on a show. I can't tell you what we could have done differently."
The warning comes four years to the day after Brazil overcame Spain in a thrilling game at the Maracana.
Fred scored twice - memorably, one of them from a prone position three yards from goal - and Neymar got the other as Brazil put paid to the Spaniards, who were then both World and European champions, seeming invincibility.
His experienced voice will be of interest to both of Sunday's finalists in St. Petersburg.
World Champions Germany have cruised through the early matches, even though they left most of their first-team squad at home to rest.
Chile, meanwhile, are present at the competition ahead of more illustrious neighbours Brazil, Argentina and Uruguay, and are enjoying a golden era, having won the Copa America in 2015 and the Centenary Copa America in 2016.
"Being at the Confederations Cup is a unique experience, a gift that falls into your hands, and you need to take advantage," Fred said.
"It's not exactly advice," he said when asked to give advice to Sunday's finalists, "but more my life's belief: if you are going to do something, do it the best you can and that way you'll always be improving and your chances of being successful are higher."
(Editing by Andrew Heavens)
