The difference in quality of your weakest link and the rest of your squad has to be significantly high for it to be guaranteed that you get a player in that position that's why I usually buy a four star player from auctions and play him in the position where I want recommended. My starting 11 currently has 4 8star players,3 7star players, 2 6star players above 110% and my 2 central defenders at 102% each.
I've gotten only DC recommendation all season