The Roma right-back started the Selecao's 1-0 friendly win over Colombia on Friday night and even drew praise from new coach Dunga for an impressive display.
However, Maicon has now been dropped from the panel to play Ecuador on September 10 without any explanation and replaced by Monaco defender Fabinho.
"Today he has been removed from the squad," Brazil General Coordinator Gilmar Rinaldi told reporters on Sunday. "I want to thank him for the services provided to the Selecao.
"It was an internal problem. I will not answer questions about it and would kindly ask that the players are not asked about it."
The 33-year-old Maicon had only just re-established himself as Brazil's first-choice right-back.