KP's value in a trade seems to be negative right now. Trading him now means bringing back nothing of value.
Keeping him when he can't play is pretty much the same thing. So you either bring nothing on a player, or have him be completely unreliable as an asset with knowledge that he will get hurt or sick again. I like him as a person, we would not have won the title last year without him. But now is the time to ditch him to a team desperate for a big.