The Brazilian stopper was stretchered off shortly before half-time at the Etihad Stadium after Mane caught him with a high boot. The Liverpool man was given a straight red for the challenge.
A lengthy stoppage ensued as medics attended to the 24-year-old, who had been in excellent form before his injury.
He made one fine one-on-one stop to deny Mohamed Salah, while his distribution was as powerful and accurate as ever.
After the game he tweeted: “Hi, everyone - I am well. What a fright! It was an important win for us. We are strong. Thanks for all your messages of support.”
City went on to win the game 5-0 thanks to goals from Sergio Aguero, Gabriel Jesus (two) and Leroy Sane (two) and move to 10 points from the first four Premier League games.
