De Laet was carried off on a stretcher towards the end of the Foxes' 1-0 home defeat on Saturday following a challenge from Owls midfielder Jeremy Helan, and his right leg was placed in a splint.
Leicester boss Nigel Pearson said: "I don't think there was any malice in the challenge. I have seen it again. Ritchie went to make contact with the ball and we are talking about a contact where players are moving in different directions.
"It is his right leg. It is the fibula or ankle area. It is a contact of his lower limb and the extent is unclear at the moment. We hope it isn't too serious."
Pearson may have to dip into the loan market for a right-back to cover for De Laet if the injury proves to be a long-term problem, and the manager added: "I don't know at the moment if we have to go into the loan market. It is something we might need to consider."
The Foxes, who are fifth in the Championship with 10 games to go, travel to play leaders Cardiff on Tuesday night.