People seem to be mixing up managing and coaching.
Guys like Wenger, Mourinho, Benitez, Sir Alex and Guus Hiddink had relatively unspectacular playing careers yet went on to become accomplished managers.
They however always have coaches on their staff that were quality, accomplished players in their day - Pat Rice, Boro Primorac, Liam Brady, Mike Phelan, Brian McClair, Sammy Lee, Steve Clarke, Franco Baresi etc.
There are different qualities required to run the team than there are for relating one-to-one with the players on the training pitch, where the ability to pass on experience, understanding and technique improvement is invaluable.
Glad to have him back, the boys at the back clearly need a kick up the arse from somewhere.