I'm not worried about his on field form, it's what it always has been, really nice rocks and diamonds, He's very rarely terrible, but that isn't the point. That's not what is devaluing him.
It's his off-field value. The intangible stuff that you can't track with stats and figures. There's no denying that he has a negative effect on the team, we saw that this year, now I'm not saying it was all him, there were many factors at play, but it could be rightfully assumed he played some part in it.
Then when you add the non stop media circus that follows him, and the clubs need to steer clear of any negative press for a good long while and his value begins to plummet.
If he has any brains at all, if he is cleared of this allegation, he will book it to the ESL.