Ex-NBA player Al Harrington says Zion Williamson should do one thing if he wants to have a long career dominating on the NBA level ... and that's lose about 20 pounds.
Zion has the Internet going nuts right now ... with his crazy dunk videos (including a free throw line joint) from Duke practices going viral because of the sheer amazingness of his athleticism.
But Williamson is physically MASSIVE ... with reports saying all that jumping ability is coming from a guy who weighs upwards of 280 pounds.
Harrington says that's fine for now, but if Zion wants his body to withstand the night-in, night-out grind that is the NBA, he might wanna shed a little.