Hummels headed Germany's second goal in Monday's 4-0 thrashing of Portugal in Salvador before having to be helped off with deep bruising to his right thigh.

The Borussia Dortmund centre-back now faces a race against time to be fit for Saturday's Group G clash in Fortaleza.

Right-back Jerome Boateng should be available, despite partially tearing a thumb muscle against Portugal, and will play with a splint on his right hand.

"Jerome will train as normal, Mats will follow an individual programme and will be treated throughout the day," said Flick before Germany trained on Wednesday afternoon.

"We hope that our excellent medical department can get Mats fit for Saturday."

Should Hummels miss their second group match, there are plenty of options to replace him, according to Flick, who ruled out a switch of Germany captain Philipp Lahm from midfield to the back four.

"We have enough alternatives, so Philipp Lahm will not drop back into defence, he'll stay in midfield," said Flick.