The Brazilian initially lay motionless on the turf at the Tottenham Hotspur Stadium on Tuesday while he was being treated by medical staff, with City manager Pep Guardiola later saying medical staff had told him Ederson could not see properly after Romero's leg made contact with his head.
Nevertheless, Ederson played on for several minutes before being replaced by Stefan Ortega, who made several key saves in a match City went on to win 2-0 to put themselves in position to retain the Premier League title on Sunday's final day of the season
Luke Griggs, the chief executive of the brain injury charity Headway, said: "The fundamental principle of any concussion protocol is 'if in doubt, sit it out'.
"The concern from players of both teams in the immediate aftermath of the injury, as well as from the medical team and the fact a stretcher was brought on to the pitch, would suggest a clear concern for Ederson's well-being.
"The fact that he was not immediately removed would suggest a concussion was not suspected. This is hard to understand, especially as symptoms can be delayed in their presentation."
He added: "While we were relieved to see the player taken off a few minutes later, it is hard to fathom why this was not an immediate decision.
"It is yet another example of when a temporary concussion substitute would have been helpful."
The Premier League has attempted to trial temporary concussion substitutes, but football's lawmakers have rejected this option in favour of trials of additional permanent concussion subs, which will become a permanent option for competitions to adopt from July 1.
Ederson was visibly angry after being taken off in what was a key game for City.
"Ederson's angry reaction is no surprise given the competitive nature of players who want to take part in massive games like this one, though his reaction underscores the need to take such decisions out of the players' hands," Griggs added.
Guardiola said after Tuesday's match: "Ederson has a kick in the eye and it is swollen. He could not see properly. The doctor came to me and said, 'Pep, he cannot see properly and he has to be replaced'. When the doctor says that, I don't have an alternative."
