Brazil have called up Internacional's Geferson after Real Madrid left-back Marcelo was ruled out of the Copa America.
Marcelo suffered a back injury with AS reporting that Real Madrid informed Brazil earlier this week of the 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."
The 21-year-old Geferson will join Dunga's squad for the friendlies against Mexico and Honduras, before Brazil start their campaign against Peru on June 14.