Manchester City could be without Ederson for Sunday's blockbuster Premier League showdown with Liverpool after he was substituted at half-time in the 1-1 draw against Atalanta in Wednesday's Champions League match
The Brazil international did not have a shot on target to deal with during an opening period at the San Siro where City took a 1-0 lead through Raheem Sterling before Gabriel Jesus missed a penalty.
Ederson darted out of his area to make a clearance late in the half but did not appear to be in any discomfort, meaning it was a surprise to see Claudio Bravo warming up at the interval and come on for the restart.
Pep Guardiola confirmed the Brazil international had suffered an injury but wouldn't commit to his availability for the top-of-the-table clash at Anfield.
"I don't know right now - it's a muscular problem," Guardiola said post-match.
"It was not big but to avoid risk. He didn't feel comfortable in the last minutes and that's why we decided to make a substitution."
Bravo conceded the equaliser only four minutes after the restart and was then sent off with nine to play after rushing out of the area to make a challenge on Josep Ilicic.
Right-back Kyle Walker was forced to into goals as a makeshift keeper for the remainder of the match, making one save from the free kick resulting after Bravo's red card.
Despite failing to win the match, City remain top of their Champions League group with 10 points, five ahead of Shakhtar Donetsk and Dinamo Zagreb, who played out a 3-3 draw in a simultaneous game.
A point to Guardiola's team in their next European encounter at home against Shakhtar on November 26 will seal their progression to the knockout stage,
City are already without defenders Aymeric Laporte and Oleksandr Zinchenko (both knee), midfielders Rodri (hamstring) and David Silva (muscular) and winger Leroy Sane (knee).
The champions are six points behind Premier League leaders Liverpool in second after 11 matches and will be keen to get a positive result at Anfield to keep the pressure on.
It's likely that Bravo will be used in goals if Ederson fails to prove his fitness for the match.
The Brazilian custodian has played every match for City in both the Premier League and Champions League so far this season.