Some rookies are more prepared than others for their first NBA season.

And it doesn't usually play out the way it did this year, when each of 2018's top five picks could make the first-team All-Rookie squad. 

There will be top picks ready to produce in 2019-20. But a trio of upperclassmen who could land outside the lottery stand out as NBA-ready as well.

No science or formula predicts who's most equipped for NBA life right away. Some of the top athletes will need time to add more skill and basketball IQ, like Ja Morant. And some of the more skilled players will require experience and physical growth, like Vanderbilt's Darius Garland. 

For specific, individual reasons, these six players could become valued contributors to their teams as rookies.

Zion Williamson (Duke, PF/C, Freshman)

Draft projection: No. 1 overall

The 2019 lottery winner will add an immediate force in Zion Williamson.

Jumping from college to the NBA won't limit the effectiveness of his unprecedented package of power, quickness and explosion. It will still create a special advantage in transition and the paint on drives, cuts, low post-ups and offensive rebounds. 

After leading the nation in points per game around the basket (10.0), per Synergy Sports, he figures to continue positioning himself for easy buckets by beating rim protection with speed, strength, bounce, a second jump and motor. And though only listed at 6'7", there isn't a pro outside of 7'3" Boban Marjanovic who can match Williamson's 285-pound frame, which he operates with similar burst and quick-twitch movement as the game's top guards.

His remarkable foot speed, springs and competitiveness should also work defensively, even if he makes mistakes gambling or rotating early on. He'll remain tough to shake in space and a threat to jump a passing lane or elevate for a block.

Creating quality shots for himself off the dribble in the half court could take longer. And he's likely to struggle from behind the NBA's three-point arc. 

However, he should possess enough off-the-dribble wiggle and shot-making improvisation to execute in certain one-on-one battles as a rookie. He generated 1.312 points per possessions on post-ups (99th percentile), 1.273 PPP on 22 pick-and-roll ball-handling possessions (99th percentile) and 1.040 PPP out of isolation (87th percentile).

Regardless, Williamson won't need advanced skill to apply significant pressure at both ends. He'll be the easy Rookie of the Year favorite following the draft.

RJ Barrett (Duke, SG, Freshman)

Draft projection: Top three

One of the top-producing freshman over the past two decades, RJ Barrett should have enough moves, shots and instincts to score as a rookie.

For a pro 2-guard, he'll also have solid positional tools to continue executing against NBA defenses, with a profile—6'7", 202 lbs, 6'10" wingspan—that's almost identical to Caris LeVert's (6'7", 204 lbs, 6'10" wingspan). 

Barrett's skill set may require fine-tuning in terms of shot-creation, but since high school, he's demonstrated a knack for finding a window or adjusting with improvisation to finish from unconventional angles. He also hit 73 three-pointers through 38 games, appearing confident and dangerous when set and able to step into rhythm jumpers.

Barrett could even add some value as a ball-screen facilitator, an underrated aspect of his game overshadowed by occasional tunnel vision that's driven a narrative painting him as selfish. Of the 38 shots taken on his pick-and-roll passes to roll men and cutters, 30 were converted into baskets. 

For rookie efficiency, he'd benefit by landing with a team that could immediately surround him with established scorers. His field-goal mark could be notably higher if he goes to the Chicago Bulls or Atlanta Hawks versus the Cleveland Cavaliers.

De'Andre Hunter (Virginia, SF/PF, Sophomore)

Draft projection: Top 10

While the height of De'Andre Hunter's ceiling is in question, teams that scouted the national title game likely saw a forward they could plug right in next season. 

Hunter, whose body—6'7", 225 lbs, 7'2" wingspan—nearly mirrors Kawhi Leonard's (6'7", 230 lbs, 7'3" wingspan), helped hold projected top-10 pick Jarrett Culver to 5-of-22 shooting. The ACC Defensive Player of the Year looks ready to compete physically at the NBA level, but he also possesses the IQ to make reads and adjustments. 

He could be the rare rookie forward valued more for his defensive effectiveness/versatility. He'll still offer enough offensively to justify regular minutes after shooting 43.8 percent from three. And though not known for his one-on-one game or off-the-dribble ability, Hunter's skill level did jump this season, with the sophomore converting 21 of 40 post-ups (88th percentile) and 25 of 57 shots out of isolation (75th percentile).

Still, he'll work mostly off the ball next season, spot-up shooting, attacking closeouts with line drives and crashing the offensive glass. 

Regardless of where he ends up, Hunter, a fit for any roster, should already look like a good bet to finish first-team All-Rookie, even if his stats aren't overly exciting. 

Brandon Clarke (Gonzaga, PF, Junior)

Draft projection: Top 20

Brandon Clarke shouldn't have to make any adjustments moving from college to the NBA, where he'll be asked to play the same role he occupied at Gonzaga.

He won't need skill next season to produce—just the same active, springy legs to run and jump in transition, on cuts, missed shots and rolls to the basket. The 6'8" 22-year-old, whose 37.0 player efficiency rating would have been the highest in a decade if Zion Williamson didn't exist, will continue playing to his strengths as an off-ball finisher and energizer. 

Clarke isn't a complete non-threat with the ball, however, showing touch around the key (39-of-64 on post-ups) and the ability to attack closeouts (9-of-13 on drives to basket out of spot-ups).

He's still bound to make more rookie noise with defensive playmaking and versatility. His analytics profile is tough to beat—Clarke finished No. 1 or 2 in the nation in defensive box plus-minus, defensive win shares and defensive rating. And he managed to rack up 3.1 blocks and 1.2 steals in only 28.1 minutes per game. 

Numbers aside, Clarke's exceptional mobility and bounce, powered by intensity and fearlessness, can still translate to immediate defensive plays on the ball and switching.

Grant Williams (Tennessee, PF, Junior)

Draft projection: First round

Lottery teams will presumably look past Grant Williams, a junior without plus athleticism or mismatch size. He's a value pick waiting to happen. 

Whoever drafts Williams can immediately use him in the post, where he'll hold his own with a 236-pound frame, exceptional footwork and passing instincts. He shot 50.0 percent from the left block, 53.7 percent from the right block and 71.4 percent on flashes to the middle of the paint. Williams compensates for below-average height at the position with surprising elevation and a super-high release point. 

Teammates also converted 46.2 percent on his passes from the post. 

Offensively, he doesn't operate from everywhere or with flashy, face-up wiggle. But he's extremely proficient in his sweet spots around the key. And he should have enough strength, length, skill level and IQ to continue executing his bread and butter.

His coach should also feel comfortable playing Williams based on his defensive awareness and versatility. He's an anticipator and savvy. Opponents generated just 0.628 points per possession against him in the post (83rd percentile). And despite his wide, heavier body, he moves his feet well around the perimeter, showing impressive lateral quickness to close out, contain in space and switch.

Williams won't wind up earning Rookie of the Year votes, but he could finish among the leaders in minutes, efficiency and impact.

Cameron Johnson (North Carolina, SF, Senior)

Draft projection: First round

Cameron Johnson blew up into one of the nation's top shooters. And the right NBA team could immediately optimize his valued, speciality skill of knocking down jumpers off the same actions he ran at North Carolina. 

Already 23 years old with advantageous 6'9" positional size, Johnson, who shot 45.7 percent from three, excels by shooting on spot-ups (47.7 percent) and off screens (55.2 percent).

And despite lacking athleticism, he scored 157 points (36 games) in transition (1.236 PPP, 83rd percentile), giving UNC's guards a quick-trigger target to find on the wings before defenses could set.

His ability to catch, square up and release with speed and fluidity resembles a pro shooter.

Johnson won't be handling the ball or creating, but on a more open, spaced NBA floor, his shot-making should translate right away.

Stats courtesy of Synergy Sports, Sports Reference.