Brazil just need a draw against Serbia in their final group game to progress.
The Brazilian Football Confederation (CBF) said in a brief statement Danilo had complained of pain around his hip during Thursday's training session.
They won't have it easy against the Swiss however, as Vladimir Petković's side took on their toughest opponent in their opener and came away unscathed.
"The case that is most worrying is Douglas Costa's, but Danilo's is not much different, except that his is a less important, secondary muscle, so there's a little better expectation with respect to him", he added.
Brazil fans believe their World Cup hopes have been given a boost by the news of star striker Neymar's new haircut, ditching his old blond coiffured style after it was trolled online. He did, briefly, but video review showed the Paris Saint-Germain dived.
"When I gave the ball back (to Costa Rica) he insulted me", Silva said in comments reported by globo.com.
"He had a knock, but I think it was the first time in three-and-a-half months he played 90 minutes", said Tite.
Brazil's coach Tite also commented on his players tears, suggesting they could be down to the huge pressure of leading the five-times world champions. As we publish these photos, the game is still at a scoreless tie.
The foward struggled in the opening game with Switzerland, but scored a last-minute goal for his country in their 2-0 win over Costa Rica, and Brazil team doctor Rodrigo Lasmar has confirmed he has been passed fully fit ahead of Wednesday's final group game.