Fofana sustained a fractured fibula when he was tackled by Villarreal forward Nino in the second half at the King Power Stadium on Wednesday. The France under-21 centre-back had lengthy treatment on the pitch, including being given oxygen, before he was stretchered off.
"Hello guys, many thanks for all your messages. It is a bad day today but I am in a tremendous club with a wonderful medical team," Fofana wrote on Instagram on Thursday. "I will give you news as soon as I have a final diagnosis but we already know that I have a fibula fracture. I will come soon and stronger: do not worry."
Fofana excelled for the Foxes last season after he joined from Saint-Etienne in October. He made 38 appearances as Leicester finished fifth in the Premier League and won the FA Cup for the first time in their history.
Fofana's injury is a major blow to Leicester ahead of the new Premier League season. They also play in the Community Shield against Manchester City at Wembley on Saturday.