Johnny Dixon has a suitable build for the position, in addition to being slender.
He's not an elite athlete but has enough quickness, speed, acceleration, agility, and strength to be a generally good athlete.
He has good footwork, though not to the extent of being able to keep up with smaller slots who can outmaneuver him due to their quickness and acceleration capabilities.
Skill wise, he's adequate, even good at times; Dixon has a good backpedal, demonstrates patience before opening his hips, and his transitions are also adequate.

In press, Dixon can jam the opposing receiver, his footwork is quite skilled, allowing him to not be fooled by the receivers' releases and thus mirror them.
He's even very good against TEs, where physically they don't necessarily get the upper hand on him.
The main problem is in off-man, where he allows too much space on short inside routes between him and the receiver, enabling catches. Even though his closing speed is interesting for his build, it's not elite. He often opts not to concede a big play but potentially allows some smaller ones.
He has issues keeping his eyes on the QB and can be manipulated by the QB and receiver.
He lacks the necessary recovery speed when his counterpart has made a difference, and he tends to be very grabby.

In zone coverage, I really like his IQ; he has good click and close and can cut off pass trajectories because he reads the QB's eyes very well.
He has enough explosiveness to leverage his very good reads and make big plays.

Dixon has good ball skills, with good eye/foot/hand coordination and long arms, allowing him to consistently play the ball. His ball tracking is also quite good, even with his back to the play.

Dixon is a true asset against the run game, putting in a lot of effort, possessing the technique to shed blocks, and clean tackling technique, though his lack of power is noticeable. 
He's very interesting in blitzes off the edge, probably one of the best in this class, if not the best. He has good understanding, very good agility and upper body flexibility, in addition to being able to take good pursuit angles.

Johnny Dixon is a decently athletic, versatile prospect with good football IQ and very interesting skills in zone coverage and against the run game.
He was quite good against Marvin Harrison Jr when lined up against him and did very good work against quality TEs.
I don't think he has much room for improvement, but Dixon could be a real asset in a defense; he can easily be a no. 3 who can be given some freedom and seen in various packages, or even included as a Safety if he gains muscle mass and strength.
I evaluate Johnny Dixon as a fourth-round prospect.