He's not cooked but Erik Ten Hag threw the midfield tactically under the bus last season with the spaces exposed between the midfield and defence.
Posted in multiple threads that from a defensive standpoint a prime Casmeiro and Kane would be incapable of providing cover. Erik single handedly was the sole contribution for the poor midfield, it's the worst set of tactical fluency I have seen of any manager post SAF it was diabolical.
Evidence of this is Amrabat, awful all season yet the last three games when the team reverted to the double pivot which resembled the shape of a 4-2-2-2 he looked a new signing totally different player. Casemiro was sublime last season in the same set of circumstances when partnering Eriksen.
He should be sold from an economic standpoint but it's far from a situation where a player could regress so drastically in a few months coincidentally when the manager employed a suicidal system all season.