You can try to sell them to the players, but, if they want they can take those domain names from you without paying you.

This happened many times when people tried to sell domain names to celebrities. It's much easier for Tom Brady to prove that he has more rights to the name tombrady.com than to you to prove you have some "rights" to it (just an example.)

I dont understand what the point of having them would be. I would say sell them to a diehard fan and get some money off of them.

wait until they wanna buy them and then sell them?

burn them***

Try to give them to the athletes free of charge or cancel the names. What you are doing is cybersquatting and could get you into legal problems very quickly.