He's slow footed but makes up for it by being long, having quick hands and being active. Allen went by him everytime like he wasn't there. Go watch the game again. One or two dribbles and he was by him with Jackson chasing him like he missed the school bus. Same could be said for others, too.
Also, it's really hard to swallow calling someone a great defender when the guy they were primarily defending went off for 37. Unless someone wants to chart Allen's percentage against AJ as an iso, go for it. Otherwise, I'm tired of hearing about it.