tackling, marking, positioning, pace and acceleration i prefer to be half decent (at least 12), concentration, decisions, anticipation, determination, heading, jumping, strength, all of these should be good for a top defender i think
 
All the ones Eddie Money said. A good way to find out which attributes are important is to click on that position on your tactics screen, the important attributes will be highlighted. Or you could create a search filter from someone like Terry or Ferdinand (or Coloccini
 
I look for the following attributes for CDs:
1. Height >186 cm.
2. Good mental stats
3. Acceleration > 12
 
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