City take on Mourinho's side on Wednesday knowing that they must win their remaining two matches to have any chance of making the last 16.
But Mourinho said: "I think they can win tomorrow, of course they can, and they can also win in Dortmund, why not, but eight points is not enough.
"I think they are out for a second time and that must be difficult for them."
Mourinho will become the youngest coach to take charge of 100 Champions League matches on Wednesday and only the fifth manager to reach the milestone after Carlo Ancelotti, Arsene Wenger, Ottmar Hitzfeld and Sir Alex Ferguson.
And while the former Chelsea boss expects City to go out in the group stages for a second consecutive year, he still sees them as potential winners of the competition in the future.
"I think they are a team to win the competition - one of the teams to win the competition," he said.
"I don't think it is normal when you are out of the competition at the very early stage.
"I speak for myself. If Real Madrid loses a final or semi-final, or even a quarter-final, that is football.
"When you are out at the group phase it is more difficult to accept and understand.
"But this is a very difficult group. Since the beginning we knew a big team is out, probably two.
"Other teams are playing easy groups and have known from day one they would qualify easily.
"City, Real Madrid and Borussia all want to win the competition, we all can, but we all know we can be out in the group stage, especially as Ajax are also taking points and have some ambitions."