"Nasri has a serious injury with his knee - it was directly a red card. Maybe it's medial ligaments. We'll see tomorrow what happens with him."
The 26-year-old French international, who should be named in France's World Cup squad this year, was writhing in pain on the pitch before being carried off on a stretcher after a six-minute stoppage in play as he was treated.
He left the ground on the team coach with his knee in a brace and his immediate future in doubt after the hack which earned Yanga-Mbiwa only a yellow card from referee Mike Jones who endured a torrid afternoon.
Earlier, he incensed Newcastle manager Alan Pardew by overruling his assistant to disallow Cheick Tiote's 20-metre volley, ruling that Yoan Gouffran had unsighted City keeper Joe Hart.
Pardew said the goal should have stood because Gouffran did not unsight the keeper even if he was in an offside position.
City won with goals from Edin Dzeko after eight minutes and Alvaro Negredo five minutes into the stoppage time added for Nasri's treatment.
The result took City back to the top of the Premier League, at least until Arsenal play Aston Villa on Monday.
(Reporting by Mike Collett, editing by Ed Osmond)
