NBA draft busts emerge every season due to misevaluations by teams or prospects' failures to catch on.

Busts must also be determined relative to where players are selected; those picked in the 20s—or later—won't have major expectations. 

The following prospects could all receive looks from lottery teams, and going that early would naturally raise the bar for their NBA outlooks. However, questions about their particular skill sets or bodies should cause hesitation about their fits and long-term values.

Bol Bol (Oregon, C, Freshman)

Bol Bol lasted nine games before he suffered a stress fracture in a foot that anchors one of his skinny legs and a 7'2" body.

Teams anxiously await medical reports and doctors' opinions regarding his current and future health. Will his feet hold up? How will his thin frame handle the physicality delivered by NBA centers? 

Bol isn't difficult to move under the basket. Despite his massive 7'8" wingspan, he wasn't the impact defender his 2.7 blocks per game may have suggested. His sense of urgency fluctuated. His awareness wasn't always sharp. 

Though he's highly skilled, it's also reasonable to question how well he'll execute the flashes of ball-handling moves and jump shots he briefly showed at Oregon. Is he sharp and fluid enough to shake free? Was the small sample size of shooting accuracy legitimate? 

Bol could wind up a top-five player from the 2019 class if he answers questions about durability, strength and motor. But his floor is also that of a draft bust.

Rui Hachimura (Gonzaga, PF, Junior)

The Nos. 15-30 range sounds more reasonable than the lottery or top 10 for Rui Hachimura, though it's possible he goes early if one team buys into his 19.7 points per game on 59.1 percent shooting from the field.

From an NBA perspective, his fit at the next level is questionable despite a dominant season at Gonzaga. Worrisome shades of Jabari Parker have ultimately made us hesitant to push Hachimura up our draft board.

After three years, he's still a shooter with limited range who made just 0.5 threes per 40 minutes and 29 percent of his two-point attempts beyond 17 feet as a junior. Will he ever add distance to his line-drive shot?

He's also lacking other ancillary skills and strengths for role-playing purposes.

His passing IQ is low, leading to missed reads and a poor 9.1 assist percentage. At 6'8", 230 pounds, he grabs just 8.6 rebounds per 40 minutes. His effort on defense also fluctuates, and though he flashes glimpses of ability when switching or containing, his 1.7 steal percentage and 2.4 block percentage are discouraging indicators for an athlete of his caliber playing against mid-major opponents.

Like Parker, Hachimura can be tough from the elbows and post, but his margin for error as a scorer won't be high. How well will he fit if he can't stretch the floor, find teammates or add value as a rebounder and defender?

Keldon Johnson (Kentucky, SG/SF, Freshman)

Keldon Johnson looks the part with his solid 6'6", 211-pound frame and athleticism. He passes the eye test from a physical perspective, which may hint at lower risk to some teams. 

But will his game translate? 

He showed minimal ability to create his own offense, raising questions as to whether coaches will want to play him as a guard. Johnson totaled just six field goals all season out of isolation and pick-and-rolls combined. His 10.5 assist percentage is red-flag low for a perimeter player. 

Johnson's power and aggression suit him when he attacks downhill, but he hasn't demonstrated convincing finishing instincts around the basket (53.2 percent), even struggling in transition (1.017 points per possession, 49th percentile).

And though shooting 38.1 percent from three seems encouraging, he only converted 1.6 threes per 40 minutes and made just 32.7 of his triples during conference play. Based on his non-shooter status in high school, plus this year's small sample of made jumpers, a 70.3 free-throw percentage and a drop-off in accuracy during the final two months, caution signs should pop up. 

His best shot is the runner (25-of-58) around the key, which will be useful. But for a wing, poor creating and playmaking ability will put pressure on his jump shot, and I'm not sold it will be accurate enough. The 20s would be a safer range to draft Johnson than the lottery.

Nassir Little (North Carolina, SF/PF, Freshman)

One team is bound to overlook Nassir Little's freshman year for the long-term potential flashed through high school and spurts of college. 

After he earned just 18.2 minutes per game at North Carolina, I'd hesitate before handing him a pass. 

Little struggled with his limited opportunities to create, generating 0.667 points per possession on 33 isolation possessions (31st percentile) and 0.556 PPP on 18 pick-and-roll ball-handling possessions (18th percentile). He converted six post-ups all season. 

He also totaled just 24 assists through 36 games, showing no signs of playmaking ability. 

Little couldn't make shots playing off the ball, either. He went 9-of-38 on spot-up jumpers and 14-of-52 on three-pointers.

The 6'6", 220-pound forward has an impressive physical profile, which buys him time to develop. However, his skill and feel lag far behind. Unless he makes dramatic improvements to his ball-handling, shooting and passing, it's difficult to picture the area of the game in which he'll add enough value to neutralize his limitations.

KZ Okpala (Stanford, SF, Sophomore)

The idea of KZ Okpala is appealing. An athletic 6'9" wing or small-ball 4, he could look extra enticing during workouts, particularly after he took a step forward to average 16.9 points as a sophomore. It may all lead to a team reaching for potential and betting on his development. 

But is there enough substance behind the production and ceiling that suggests he'll become a mismatch scorer?

Okpala isn't a polished shot-creator, having converted just 12-of-32 looks out of isolation. He shot an ugly 9-of-35 on dribble jump shots in the half court. And he wasn't efficient around the basket, where he made 51.6 percent of his attempts and grabbed just seven rebounds per 40 minutes.

His frame doesn't look suited to plow through contact in the paint. And though Okpala's outside shooting improved, it's still far from a strength. He made just 1.4 threes per 40 minutes and connected on only 67.1 percent of his free throws.

At this stage, he's missing a reliable skill or strength. He also doesn't seem close enough in any one area to feel confident in his trajectory or fit in today's NBA. 

Stats courtesy of Synergy Sports, Sports-Reference.com