Nkounkou probably should have been used as a left winger rather than as a left-back. His attacking attributes (especially his dribbling) vastly outweighed his defensive qualities. Decent player who will probably have a steady yet not spectacular...
What are doing to ‘convince ‘ him ?
Hanging him off tower blocks by his legs.
Carrying baseball bats into meetings.
Kidnapping his dogs and and handing him one of their ears ?