Here's from a pretty old guide (but I still find it useful):

Using a player outside their natural position should be avoided whenever possible, but isn’t the end of the world as long as it’s not too far away from that position vertically or horizontally (but not in diagonal, except for strikers).

So a DMC will make a decent DC, DML, DMR and MC and a ST will make a decent AMC, AML and AMR. Just don’t do this too often or the player’s form will drop.
http://forum.topeleven.com/tutorials...-opponent.html

Maybe things have changed. But if you are going to use your player out of position, remember to keep an eye on his form.