The Chelsea winger sustained a knock in training on Saturday and there were concerns over his availability for the clash in Belo Horizonte.
With Neymar ruled out of the rest of the tournament due to a fractured vertebra, the sight of Willian limping out of training was another blow for the host nation as he was seen to be a potential replacement for the Barcelona forward.
The 25-year-old eased fears over his fitness at a press conference on Sunday, though, and revealed that he would be back in training on Sunday.
"I am feeling great. I was hurt on my left side in training yesterday (Saturday) and it bothers me a bit but it is nothing significant and it won't stop me training today," he said.
Brazil midfielder Luiz Gustavo is set to return against Germany after being suspended for the quarter-final win over Colombia.
Meanwhile, FIFA have confirmed that the hosts have lodged appeal against captain Thiago Silva's one-match ban after the defender was shown his second yellow card of the tournament on Friday.
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