Which player should I use as my DR?

Hello, my DR and one of my DC s can play DC/DR. But i cant decide which one should I make my DR and DC. I got Silva from the scout. I use him as my DC right now but i can use him as my DR, too. Where do you think he will play better ? I play 4-5-1 V style, i heard this formation needs good wingers so should I make Silva my DR? here is my formation:

http://i.imgur.com/ePzaa9q.jpg

Trail & error.
Play him 3-4 games as DC and see his ratings, play him as DR and do the same ^^ I would probabbly leave him as DC but i would still try to find out where would he perform better.

Play him against stronger opponent, if it is ST then play him as DC, and if it's AML then play him as DR...