"Mario will have an operation in a few days," Platt told City's website after the 3-1 home victory over Queens Park Rangers in the English Premier League.
"It's not a major procedure and he should be back quite quickly. I've heard suggestions he will be out for a month but that's not true.
"Hopefully it will correct a problem he's been having for some time and he can move on from there," added Platt.
Bobby Zamora [ Images ] was on target for the visitors in the second half.
City are fourth in the league, two points behind leaders Chelsea [ Images ], with seven points from three matches.
Photograph: Claudio Villa/Getty Images