Yes you can, you go onto edit mode, choose teams from the list, then register player, then select the team you wish to put the player into, and at the top of the list of players will be an "add" button, press that and then choose the team in which the player is in at the time, then choose the player and agree to assigning him to the side. If the player is not at a club, then he will be in his national side unless he has retired/not been called up for national duty.
Here is a list of team name changes and transfers that were not done -
http://www.cheatcc.com/xbox360/proevolutionsoc cer2009cheatscodes.html