The Argentina defender suffered a hamstring strain during Thursday night's 1-1 Europa League draw with Juventus at Eastlands which Mancini believes is serious enough to make sure he is not involved against the Magpies.
"It is a hamstring," said Mancini. "I do not believe it is serious but he won't play on Sunday."
At least Jerome Boateng came through his first City start unscathed, although Mancini might be loathe to risk the German international after so long out with a knee injury.
The medical bulletin was of more significance than the game itself, which turned into a stalemate once Juventus' early fire had been doused.
"I don't know why we started so slowly," said Mancini.
"We thought we could control the game but after Juventus scored, the match changed. Sometimes that can happen when you have to play every three days."
Vincenzo Iaquinta put Juventus ahead when his 30-yard shot took the faintest touch off Kolo Toure which proved to be enough to get it past Joe Hart. After an initial struggle, Adam Johnson levelled for City before the break when he collected Yaya Toure's sublime pass and beat former Arsenal keeper Alex Manninger from close range.
Now Mancini must patch up his troops and try to build on last Saturday's victory over Chelsea when Chris Hughton brings his Magpies south. It will not be easy, with the Italian admitting Carlos Tevez in particular needs a break.
"I am concerned about the situation," he said. "If we had all our strikers available probably sometimes Carlos could miss a game. But we knew we would have a problem with injuries until the end of this month."
Source: PA
Source: PA