The 22-year-old midfielder is currently on loan with German second division side Greuther Furth, but has been on the sidelines since October after managing just four appearances for his loan side.
Ideguchi suffered the same injury as sustained by Leeds striker Patrick Bamford - a tear of the posterior cruciate ligament. The problem is expected more in the likes of car crashes.
Furth's decision was not to operate on the Japan international, and instead create more muscle - or protection - around the ligament to help it grow and recover, without having to go under the knife.
It is a process that worked for Wolfsburg midfielder Joshua Guilavogui, who returned in just over eight weeks. An operation can leave you sidelined for four months or more, as Bamford has found out.
However, Furth, Ideguchi and Leeds will have been wishing that they had decided to put the struggling midfielder into theatre, as he is suffering more discomfort in his knee and may now have to undergo surgery - three months later.
Ideguchi is yet to make a single appearance for Leeds, after he joined Cultural Leonesa after joining the Whites last season on loan. He did appear in pre-season before joining Furth. His Leeds contract ends in 2022.
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