Add the following codes as a last name, when your creating a player and it will unlock them for you. They are then available in the "Free Agent Pool". Copy the codes exactly as they are.

posneghx - Mario Austin
skenxido - Malick Badiane
zxccvdri - Sani Becirovic
bbvdkcvm - Matt Bonner
sdfgurkl - Carlos Delfino