The Foxes, who have won seven of their 10 games under former England boss Sven Goran-Eriksson since the turn of the year, currently sit just outside the Championship play-off places and Warnock is expecting a tough afternoon.
Warnock said: "Leicester will be our most difficult game of the season. They're absolutely flying at the moment and we're going to have to come up with the right answers to get something from the game.
"We've got 12 matches remaining, six at home and six away, but we'll continue to take one at a time.
"I'm really pleased we've got a full week this week. Danny Shittu and Fitz Hall have done magnificently, but they'll need a break.
"We've got to be ready for Leicester, and so have the crowd. It's looking like it'll be a sell out and our fans need to take the roof off Loftus Road between now and the end of the season."