I'm dismissive of it because it's not very good and hasn't been since he arrived. Every player has weaknesses. That's absolutely one of his. But by all means I hope he proves me wrong. That would be some progress for him though.
Exactly this. Defensive numbers are notoriously difficult for statisticians to deal with because they're really hard to give a context to (the classic example being the Maldini tackling example). Duffy, statistically at least, is an excellent defender. But having watched him for 3 seasons...