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What fuels long-term potential before the NBA draft?

Traditionally, it's tools and athleticism, which create mismatches and allow players to make plays that don't require a great deal of skill. Even when Milwaukee Bucks star Giannis Antetokounmpo first entered the league, he was able to get himself easy baskets just by tapping into his agility, length and leaping ability at 6'11".

Then his skills caught up, and now he's viewed as one of the game's toughest covers.

The prospects with the most upside have the greatest combination of size (for the position), burst, skill level and youth, which reflects room to improve.

Arizona's Lauri Markkanen and France's Frank Ntilikina are top-10 prospects on my big board, but that's mostly due to their floors—not their ceilings. Markkanen's lack of explosiveness and defense and Ntilikina's subtle playmaking attack appear to limit their perceived upside, though both look like surefire NBA players who don't offer great risk.

Some of the following prospects come with greater bust potential than Markkanen and Ntilikina but also a greater chance to reach NBA stardom.