The hosts created numerous chances but lacked a cutting edge and manager Mancini was again left to bemoan his side's wastefulness.
The Italian said: "I think we deserved to win but when you are in the last two or three minutes of extra time, it could be difficult.
"These games, if you don't score in the first half when you have a lot of chances to score, I think they can be strong.
"They played well, they defended well, for 90 minutes with all players behind the ball. We didn't find space to score.
"When you have one chance, you have to score. In the end, I am happy with the victory but we had a big problem."