The midfielder admits Bayern Munich are likely to top Group D, leaving the two clubs - who face each other on Wednesday and November 5 - vying for the final qualification spot
City travel to the Arena Khimki on Wednesday to take on Leonid Slutsky's men, with both teams boasting one win and one loss from their opening two fixtures, before a return trip on November 5.
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"We knew that the two games against CSKA would be like finals because, with respect to Plzen, they are the team who will most likely finish fourth and second spot will probably be between us and CSKA," he told City's official website.
"When they played Bayern Munich, they really tried to play some good stuff but because they conceded a goal very early on, it was difficult for them after that."
Nasri is expecting a tough test in Russia, and warned his team-mates not to underestimate CSKA's strengths.
"I don't think they will change the way play, especially as they are at home, and they have some very good players who are quick up front so it should be an interesting contest," he continued.
"There are many good teams in Russia who try to play football, like we do. If we come back from Moscow with a win, we will have done 50 per cent of the job and we would then have a home game against them to come."