Disagree, i think he does. Problem is he's young and being young he makes mental mistakes. Also i'm not going to judge him too harshly under Martinez who obviously doesn't have a clue how to coach defence.
Reckon he'll have a better time of it under Koeman, assuming he stays of course.
no one with any defensive instincts tries doing cruyff turns in his own fucking penalty area. He always seems more focused on showing yes he's a good footballer at the cost of doing whats right defensively. Now your right Martinez could have (and probably did) had a major impact on this but I have trouble ever seeing him as even a competent defender let alone a good one.
When to play the ball in defence can be learnt. Showed more than enough the season before last to show he does have defensive ability. Could be fantastic if developed correctly.