If Lebron can somehow win this series, with the team that he has left over after 3/5ths of their starting lineup is out for the year, then he is the greatest player of all time.
You can argue all you want, but he will literally be doing this on his own. It's still a big if as to whether they can win it, but should he be able to pull this off, then he is the greatest.
Look at who he is going to battle with. Are you kidding me?