Looking at Moreno's style, I think Lee Kang-in is indeed a super-sub.

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Moreno's tactics are basically high pressing, ball recovery, and fast attacks.
Lee Kang-in doesn't fit any of those three.
It would be different if he brought out a tactic centered around Lee Kang-in,
but the problem isn't just the tactics; there are no players to actually execute them either.
As it stands, I think bringing him on in the second half to just click through crosses is the right choice.
If Moreno gets sacked and a different manager comes in, who knows,
but I wonder if it's even possible.