Eriksson is concerned City - already without Micah Richards - could be left short at the back with Dunne's injury, which may keep him out for up to two weeks.
He said: "For the last 10 minutes, you could see that Michael Ball was not okay either, you could see that for the second goal.
"But we do not have any more defenders, so we have to carry on."
The Swede, however, remains positive City can end the season on a high.
He said: "It is a difficult and frustrating time because we have taken only one point and conceded easy goals which at the first half of the season Manchester City would never have done.
"It is up to us to make it right and start to win, because otherwise there is no meaning talking about Europe.
"As long as it is still a mathematical possibility, we have to believe it and fight for it."