Ederson was withdrawn at half-time during City's 1-1 draw with Atalanta on Wednesday in the Champions League.
The Brazilian was replaced by Claudio Bravo at the interval in Milan, before Kyle Walker was forced in goal after Bravo was sent off for a sliding tackle on Josip Ilicic outside the box.
Ederson played every game of City's successful title defence last season, keeping 20 clean sheets along the way. He has also started every league and European game for City so far this season.
City have the chance to reduce Liverpool's six-point lead at the top of the table when the side's meet at 16:30 on Sunday.