Galatasaray skipper Muslera suffers double leg fracture
The 33-year-old will undergo additional examinations Monday and "an operation will be planned accordingly", the club added, without saying how long he would be unavailable.
Muslera, who has been with Galatasaray since 2011, was injured in a first-half collision with Rizespor's Czech striker Milan Skoda.
Skoda apologised on Twitter. "I'm really sorry. I sincerely hope that you will recover as soon as possible and you will be back healthy on the pitch. Winning was important to us, but I would trade it for your health," he tweeted.
Galatasaray's defeat left them third in the table, six points behind Trabzonspor at the top, and Basaksehir.
The Turkish Super Lig resumed Friday behind closed doors after a nearly three-month suspension because of the coronavirus pandemic.