Maddison sustained a knock during City's 1-1 Carabao Cup semi-final draw with Aston Villa on Wednesday night, but after undergoing tests boss Brendan Rodgers has confirmed he is clear to play.
Daniel Amartey will undergo surgery on an ankle injury next week and is set for a lengthy spell on the sidelines, while fellow defender Wes Morgan is expected to return to training next week after sustaining a groin injury in last weekend's FA Cup win over Wigan. Wilfred Ndidi is out for a few weeks after undergoing a successful knee operation.
Southampton boss Ralph Hasenhuttl has no fresh selection concerns and could revert to the starting XI which beat Tottenham on New Year's Day.
Hasenhuttl made 10 changes to his team for last weekend's FA Cup third-round victory over Huddersfield.
Right-back Yan Valery, who has been suffering with an infection and not featured since late November, remains sidelined.
Leicester provisional squad: Schmeichel, Ward, Jakupovic, Chilwell, Justin, Pereira, Evans, Fuchs, Benkovic, Soyuncu, Gray, Praet, Tielemans, Mendy, Maddison, Albrighton, Barnes, Choudhury, Mendy, Perez, Vardy, Iheanacho.
Southampton provisional squad: McCarthy, Soares, Stephens, Bednarek, Bertrand, Djenepo, Ward-Prowse, Armstrong, Redmond, Hojbjerg, Ings, Gunn, Yoshida, Vestergaard, Romeu, Long, Adams, Obafemi.