What is the cause of Lee Kang-in's slump in the national team?

The fact that we don't win when Lee Kang-in plays
It is too much of a contrast in terms of performance to dismiss it as mere coincidence
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1. Is it a lack of individual capability on Lee Kang-in's part?
2. Is it a lack of chemistry with the national team?
3. Is it due to being ostracized?
I think the second possibility is the most likely,
but since Lee Kang-in is such a difficult player to utilize,
the real problem is whether there is a manager who can actually bench him.
I am talking about a player who is a regular starter for a big club.
Hong Myung-bo failed to resolve that and collapsed.
I believe the national team currently needs a manager with a strong heart—someone who doesn't care about the eyes of sponsors or the association, and can exclude star players from the starting lineup rather than focusing on tactics.
Someone like Bielsa, for example.