Brazilian defender Lucio and midfielders Emerson and Kaka are all undergoing treatment following Tuesday's 3-0 win over Ghana, the Brazilian Football Confederation (CBF) said.
The CBF's website said on Wednesday that Emerson and Kaka both complained of pain in the right knee and that Lucio had suffered a knock on his right thigh.
It did not give any further details on the three or whether there was any risk of their missing Saturday's quarter-final against France.
Emerson was replaced by Gilberto Silva at halftime in Tuesday's game while Kaka went off in the 83rd minute. Lucio played on until the end.
It added that forward Robinho, who was ruled out of the Ghana game because of a problem with his right thigh, is undergoing intensive treatment.
Brazil are hoping that Robinho would be fit for Saturday.