The European champions were favorites to land the title in Yokohama but went down to Paolo Guerrero’s 69th-minute header.
It was no more than Corinthians deserved for a committed display, and Piazon felt the Copa Libertadores winners’ greater determination had been telling.
Brazilian Piazon, an unused substitute, told media including www.esporte.uol.com.br in his homeland: "It seems that some people are missing a few things, principally the desire to be champions.
"I think Ramires and David Luiz, the Brazilians, were the ones who strove to give their utmost, and are therefore the ones who are most upset. We lacked character and a love for the shirt. Nobody wanted the ball. At least Oscar tried. "I won’t be more specific but I can say that the team lacked willing. You don’t go into a final without the desire to play the ball, that’s unacceptable."
Piazon was, according to the reports, inconsolable in the dressing room after the game.
"I didn’t speak to anyone, I was on my own," he added. "But it seemed that David (Luiz) was feeling bad, too. He was one of a few who cared about the game."
The 18-year-old later took to Twitter to clarify his comments but continued with his belief that the South American side had "wanted the title more".
He posted on the social networking site: "All I said was that Corinthians had more courage to play the final than us, that they wanted more this title and that they played with more passion than us!
"I would never say something about my team-mates, I’m just 18 and with them I learn a lot of good things. And I also said that this title is so important for the South American clubs and that was a dream for me, that’s why I was so sad."