The 26-year-old Frenchman has been told he will be sidelined for around eight weeks after undergoing a scan following Sunday's 2-0 Barclays Premier League victory at Newcastle.
Nasri revealed the news via his Twitter account on Monday afternoon, and appeared to be relieved to have escaped greater damage.
He tweeted: "Thank you everyone for your kind words and overwhelming support, I suppose its kind of good news that I will be out around 8 weeks."
Nasri was hurt in a challenge by compatriot Mapou Yanga-Mbiwa 75 minutes into competitive game at St James' Park.
He received lengthy treatment on the pitch before leaving it on a stretcher with his left leg stabilised in a brace.
Manager Manuel Pellegrini later revealed that he had damaged his medial ligament, and claimed Yanga-Mbiwa should have been sent off rather than booked for the tackle.
Should the initial prognosis prove correct, Nasri could miss 11 games in all competitions, including Barcelona's trip to the Etihad Stadium on February 18 and the Manchester derby at Old Trafford on March 1.
When he does return, he will hope his team-mates have been able to maintain their title challenge after a gritty display on Tyneside.
The win, which came in controversial circumstances as Newcastle's Cheick Tiote was denied what would have been a first-half equaliser by referee Mike Jones, extended their unbeaten run in all competitions to 15 games.
But perhaps more significantly, it meant they have gone eight games on the road without a defeat, a stark contrast to their early-season form.
Defender Martin Demichelis told City TV: "It's true that at the beginning of the season, we didn't feel that comfortable. We were trying to get to know each other and we lost because of minimal details.
"[At Newcastle] we were lucky on those details. The players are getting to know each other more, so we really fell confident playing away now."
- Sports & Recreation
- Barclays Premier League