Aleksandar Tunchev will miss the rest of Leicester's League One campaign due to injury.
The Bulgarian defender was stretchered off the field in Leicester's FA Cup defeat to Crystal Palace on Wednesday.
He had picked up a knee problem and scans later revealed he had torn his cruciate ligament.
The news that he will play no further part this season will come as a major blow to manager Nigel Pearson.
Tunchev has made 25 appearances for the Foxes since moving to the Walkers Stadium from CSKA Sofia last summer.
His only goal for the club came in the 2-2 draw with Walsall in October.