Brazil replaced Marcelo with Geferson on Friday, with the Real Madrid defender reportedly unable to walk.
Real Madrid full-back Marcelo has been ruled out of Brazil's Copa America squad due to a back injury, with Internacional's Geferson called up as his replacement.
The Brazilian Football Confederation confirmed Geferson's promotion on Friday with a statement on their website, while AS reported that Real Madrid had informed Brazil earlier this week of Marcelo's injury problem.
"We were told by Real Madrid doctors that in a training session he went to jump and since then he's been suffering severe pain in the lumbar region," Brazil team doctor Rodrigo Lasmar told AS.
"We did some tests and he won't be able to start to train with us on Monday. He'd need around three weeks, more or less, to be able to train. Today he has real problems, he can't walk. There's no other solution."
Geferson, 21, will join Dunga's squad ahead of Brazil's friendlies against Mexico and Honduras, and he will make his senior international debut if given game-time in any of the upcoming matches.
Brazil have been grouped with Colombia, Peru and Venezuela for next month's Copa America in Chile.
Dunga's side will start their campaign against Peru on June 14.comments