If you believed you wanted to keep the player for good or for a long time, you might as well tag him as the leader of your team. Lock him to long term deals and such. But he must have a good rating because the higher his rating is, the better the morale of the team. I don't know, I noticed when I tag a created player with lower rating as the leader, players morale is very low, and they can't wait to get out of there. Some of them. But when I tag a higher rated player, my starters are happy as hell.