Foxes boss Brendan Rodgers confirmed Friday that the Nigerian international will undergo surgery and is set for a long-term spell on the treatment table.
"That (surgery) will take probably place tomorrow morning," Rodgers said. "It's just unfortunate, it's come right off the bone, so he's going to be up to 12 weeks, we think. He's a huge player for us.
"It's something that showed his mentality against Burnley (because) he felt it. Towards the end of last season, he felt some pain there and he felt it late on in the Burnley game."
Ndidi, 23, also missed a significant stretch last season following a knee operation. His absence coincided with Leicester's poor run of form that caused the club to relinquish its top-four spot.
"I'm sure he'll make a really good recovery and we'll welcome him back when he comes back, but there's no doubt he's a miss," Rodgers added.
Rodgers also said Jonny Evans has overcome a thigh concern and will return to the first-team following suspension. Ndidi had been deputizing at center-back for Leicester's two league outings in Evans' absence.
Leicester visit Manchester City on Sunday looking to maintain their perfect start to the Premier League campaign after wins over West Bromwich Albion and Burnley.