I think it might be worse.
If you do not field 5 players, it could be a walk-over, and in that case I don't think any of your players will get any minutes. Not sure about this though, I would not risk it to find out either.
I think, even if you desperatly need 4 players to get 48 minutes, you still best select 6 players...
They are not your friends; they dispise you. I am the only one you can count on. Trust me.