What makes a good-defender in Soccer?

[GeoJfreak6]

I have a friend that I know that seems kind of out of place to me on defense. He is probably 5'5" at the most and maybe 120 pounds yet he is possibly going to start on his Class 2 teams defense. He has pretty good ball-handling skills and above average speed, but is not what I would imagine as a prototypical defender. Does anyone have any thoughts on what makes a defender good in Soccer?
Thanks.

 

[last_second_shot]

gotta play smart ball ... i see defenders all the time that dont look like they should be playin that position but its about playin smart