yeah... it depends... some players works better in a different position.. I see that in all the MC players,, I play with a 4-3-3 and, when season stars and I have a new player, I have to change all players (sometimes) and put in different position..
is that...
Edeso-Van Nistelrooy-Robben.
and the next season
Van Nistelrooy- Schevchenko-Robben

and now I will buy another ST..
I will put the name Jan Vennegoor of Hesselink..
the idea is;
Van Nistelrooy-Schevchenko-of Hesselink
but...
who knows, maybe the new guy have to go in the center,
in my case during these 8 seasons I have seen that, if I have the best MC in the center of the field, he do a great work, attacking, and defending...
so maybe the center is the key in my case xD dont know...)))

just try! I think every player have a favourite position that you have to discover (^-^)