The center back is set to miss Tuesday evening's trip to QPR after suffering a fresh injury blow and will be absent for three weeks in total.
Platt feels that City must get to the bottom of the issue in order to avoid being forced to cope without its skipper.
"It is a concern that it's not a fresh injury," he told reporters.
"The calf is the strangest muscle — there is probably more recurring issues with it than with hamstrings, groins and things like that.
"And it has happened on a couple of occasions but the concern is to make sure we clear up the problem."
Kompany has made 198 appearances for City in all competitions since signing from Hamburg in the summer of 2008.