The Italian has received criticism from some quarters for failing to defend their Premier League crown, with the side currently sitting 12 points behind rivals Manchester United in second.
However, with an FA Cup semi-final on the horizon, Keegan is adamant that Mancini deserves more time at the Etihad Stadium.
"In any other sport it would be ridiculous to question someone who has gone into a football club, won the first trophy in 30-odd years, then won the league in the most exciting season ever," said Keegan. "Europe was a disappointment, but Europe was disappointing for Manchester United and Chelsea. You get that.
"You can make stories around them all you want. Is it right? No. Can it happen? Yes.
"But I don't think there should even be a question of anything happening to Mancini."
City face Chelsea in the final four of the FA Cup on Sunday.