I'm no scout but he doesn't turn his hips very well, he has a decent backpeddle and breaking speed - but he's horrible going sideline to sideline. He's awful at playing the ball in the air, going for it at its highest point, and anything else that can be described as ball skills. Which is ironic because his scouting report suggested otherwise. He also played a lot of man and press coverage in college, which you'd think would help him in the slot.
He also takes poor angles when it comes to tackling and once the ball is in the air.
I think he just the 'feel' for the position and relies on athletic ability to keep him close. And he's not the most gifted athlete either.