Richards has been told by a specialist he will be out for up to four months.
\Yet Mancini said yesterday: "I think maybe - it is my opinion - three or four weeks. I read three months but I don't know why. One month - maximum.
"It is not bad. Maybe in three or four weeks he can start to play. He put only two stitches in his knee. For this reason, maybe four weeks."
But a source close to Richards told The Sun: "There is absolutely no chance Micah will be back in such a short time.
"If he returned too quickly it would set him back another six weeks. He cannot afford to rush it."
Richards, 24, told City's own website on Tuesday: "I am probably looking at 12-16 weeks before I am back in action."