Chelsea snapped up the young Italian midfielder from Inter last summer and he spent the latter half of last season on loan at Reading.
The Blues have been keen to loan him out again in the ongoing transfer window to aid his development.
He had offers from Italy, where Lazio were keen to get their hands on Casadei this summer, but Leicester are the ones who are set to sign him.
The 20-year-old is being put through his paces during a medical at Leicester at the moment.
Leicester are looking to get him through the medical and complete the formalities of the transfer today.
They have to race against time if they want to register Casadei in the squad against Huddersfield Town on Saturday.
Enzo Maresca has been keen to have the young Italian in his squad this summer and the club are on the verge of signing him on loan.
