City's UEFA Champions League prospects are hanging by a thread after the result at the Etihad Stadium which left Mancini furious with the match officials.
The Premier League champions had fought back from 2-0 down in a gripping Group D encounter before having a goal disallowed and being denied what they thought was a penalty in the closing moments.
Mancini went onto the field to confront referee Peter Rasmussen after the final whistle and, when asked what he said, he explained: "I said it was a goal. I didn't see the last situation with Mario that was a penalty. I said it was a goal.
"The referee and his staff were really poor tonight."
The Italian's confrontation with Rasmussen could now lead to intervention from UEFA, who previously handed Arsenal boss Arsene Wenger a one-match ban after calling referee Massimo Busacca 'embarrassing' after a defeat by Barcelona in 2011.
If Mancini is given a touchline ban, he would miss City's next Champions League tie at home to Real Madrid which they must win to have any chance of progressing to the last 16.
Meanwhile, in his post-match press conference, Mancini was also asked to clarify what he said to a cameraman who followed him onto the field.
The Italian said the word 'finish' but said this was his way of asking him to stop filming and did not mean anything else.
Mancini said: "The camera wanted to film me after the game. He followed me on the pitch. I said, 'Finish, finish. Do not film me'. I told the camera to finish, go."
There appeared to be some confusion over this during the press conference and Mancini was annoyed this might be interpreted differently.
He said: "You know other words that I said? You were on the pitch with me?"