The Turkish side are up against Jose Mourinho's Blues in the Round of 16 second leg at Stamford Bridge following the 1-1 draw in Istanbul last month.
Mancini could not get former club Manchester City through to this stage of Europe's top competition in two attempts but still feels he performed well with the Eastlands outfit.
"I did a really good job with Manchester City," Mancini told reporters.
"I'm very happy to play this game, first of all because it's here in London and after because it's Champions League.
"We did a miracle in the group because it was really difficult to go through in that group.
"Chelsea have a small advantage. I don't know if it will be enough to score one goal. Tomorrow we will see what happens.
"We gave them a lot of respect in the first 20 minutes (in Istanbul). It is important tomorrow to start at the right level.
"Chelsea are a very good team, one of the best in Europe, but in football never say never so we will try."
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