Okay, so I am writing this fictional baseball book, and I want to use a living baseball legend (who is retired) as a secondary character. He wouldn't have a whole ton of appearances or dialogue, but he would be important to the plot. Are there any rules against this? Or can I just go ahead and write in a fictional version of him? I wouldn't be shedding any intentional negative light on him. Would I have to ask for some sort of permission?