Grading Top 2015 NBA Draft Prospects' Performances During College Regular Season

March Madness tournament time isn't here yet, but a jam-packed regular season is drawing to a close. It's time to hand out winter grades for the top 2015 NBA draft prospects in college hoops and overseas.

Before we dive into the inevitably volatile party that is the college postseason, let's take stock of how these youngsters have performed throughout the year. Who's been impressive enough to earn As? Who hasn't quite made the grade?

Each player's regular-season grade is based off how he produced statistically and impacted the game on both ends of the floor. We factored in traditional stats, advanced stats and execution of key skills.

How did blue-chip specimens such as Jahlil Okafor of Duke and Karl Towns of Kentucky fare? What about European stars such as Kristaps Porzingis or defensive-minded competitors such as Willie Cauley-Stein?

Find out as we break down our list of the top 10 NBA prospects. We focused on the players with the most pro appeal and consistent statistical production. They've emerged as promising assets with the best tools and skills applicable to the next level.

Prospects are listed in order of projected draft value, not their grades.

Honorable Mentions

Matt York/Associated Press

Kevon Looney, UCLA PF (6'9", Fr.): A-

UCLA's season has been tumultuous, but Kevon Looney's body of work is splendid.

His movements and skills aren't as polished as those of other top prospects, and he's not as big as forwards such as Karl-Anthony Towns and Myles Turner. Nevertheless, his stats are comparable, as Jonathan Tjarks of The Cauldron noted, "Looney’s efficiency and production for UCLA this season has been on par with both Towns and Turner."

As the calendar turned to March, Looney's stats included 15.5 points and 11.9 rebounds per 40 minutes, along with a smoldering 44 percent from long range.

Myles Turner, Texas C (6'11", Fr.): B+

Speed, agility and dazzling offensive creativity are not in Turner's tool kit. Yet scouts are drawn to him due to his pick-and-pop shooting touch and rim-protecting prowess (4.8 blocks per 40 minutes). He has churned out high per-minute numbers as a scorer and rebounder, but his inconsistent output puts a dent in his grade.

Devin Booker, Kentucky SG (6'6", Fr.): B+

Kentucky's potent off-guard has posted some outstanding shooting and passing marks this season. He has made 43.6 percent of his triples, and he's notching 20.5 points and 2.4 assists per 40 minutes. That's phenomenal considering he has to share touches with so many great players.

Frank Kaminsky, Wisconsin C (7'0", Sr.): A

A year ago, Kaminsky was just arriving on the national scene as a sure-handed stretch big. Now, he's dominating the Big Ten every night and continually solidifying his chance to land in the lottery. He's not as strong or athletic as most of his draft peers, but he's leading all D-I ballers in player efficiency rating (35.4) thanks to his refined inside-out skills and savvy.

Trey Lyles, Kentucky PF (6'10", Fr.): B

After missing three games in early February, Lyles enjoyed a recent surge that made it impossible to exclude him from our list. He registered back-to-back 18-point outings to finish the month, which gives his draft stock a boost as the postseason approaches. Although he's not a top-shelf defender or high-upside prize of Towns' caliber, he's hitting 46.2 percent of his two-point jumpers and converting 79.2 percent of his shots at the rim, per Hoop-Math.com.

10. Kelly Oubre, Kansas SF (6'7", Freshman)

Jamie Squire/Getty Images

2014-15 Stats: 20.1 MPG, 8.8 PPG, 5.0 RPG, 44.4 FG%, 38.0 3PT%, 21.9 PER

Impressive Game: 19 PTS, 9 REB, 6-of-11 FG (Jan. 19 win vs. Oklahoma)

Disappointing Game: 0 PTS, 4 REB, 19 MIN (Feb. 21 win vs. TCU)

Projected NBA Role: Shoot-and-slash swingman

Draft Range: Late lottery 

With an intriguing blend of rangy athleticism and smooth scoring skills, Kelly Oubre has kept the attention of NBA scouts despite an up-and-down freshman season at Kansas.

He cracks the list of top 10 prospects because his length and playing style are translatable to the NBA. During some stretches, he simply demolishes the eye test.

Unfortunately, "translatable" potential won't buy him a better regular-season grade. Oubre's offensive execution has been inconsistent and is still raw. In the past couple of games, he's been more aggressive, but for much of the season, he's been shaky. In Big 12 play, he's shooting 43 percent from the field and 33 percent on triples while taking just three free-throw attempts per game.

To his credit, he's been visibly more active and influential as a defender in recent weeks. It's helped him feed on transition opportunities that showcase his exquisite open-floor agility.

Don't be unsettled by Oubre's mediocre 2014-15 grade. He's shown enough flashes of talent to become a dynamic wing in the near future.

Grade: B

9. Justise Winslow, Duke SF (6'6", Freshman)

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2014-15 Stats: 29.1 MPG, 12.3 PPG, 5.8 RPG, 46.8 FG%, 39.3 3PT%, 19.6 PER

Impressive Game: 23 PTS, 9 REB, 3-of-5 3PT (Feb. 28 win vs. Syracuse)

Disappointing Game: 2 PTS, 2 REB, 1-of-6 FG (Jan. 13 loss vs. Miami)

Projected NBA Role: Explosive two-way small forward

Draft Range: Mid-to-late lottery

Justise Winslow picked a good time to start peaking.

Duke's explosive small forward has been cranking out substantial offensive numbers of late, including 15-plus points in each of his past four games. His latest performance was a 23-point, nine-rebound barrage during the Blue Devils' win over Syracuse.

"He was the best player on the floor tonight," teammate Jahlil Okafor told Chris Carlson of Syracuse.com. "When he's playing like that, it's very hard to beat us. He's a man-child. He contributed to this team a lot tonight—rebounds, blocking shots, scoring. He was a leader."

His ability to knock down threes (41 percent against ACC teams) and play above the rim doesn't automatically mean he'll be a featured scoring asset in the NBA. After all, his mid-range footwork and shooting are miles from respectable. However, it does indicate he'll get buckets within the flow of the game and supplement his team's attack.

Winslow has also served as a sharp passer in Mike Krzyzewski's system, and he rebounds well for a swingman. He's not always positionally sound on defense, but he's often Duke's most talented and disruptive stopper on the floor.

His physical supremacy and desire to contribute in every area point toward a magnificent two-way career in the pros.

Grade: B+

8. Mario Hezonja, Croatia SG/SF (6'7", 1995)

2014-15 Stats (ACB): 15.4 MPG, 5.6 PPG, 1.4 APG, 50.0 FG%, 43.9 3PT%

2014-15 Stats (Euroleague): 17.8 MPG, 8.6 PPG, 1.3 APG, 48.4 FG%, 41.2 3PT%

Impressive Game: 24 PTS, 6 AST, 8-of-8 3PT (Feb. 1 win vs. La Bruixa d'Or)

Disappointing Game: 3 PTS, 3 TO, 15 MIN (Nov. 23 win at Fuenlabrada)

Projected NBA Role: Explosive scoring wing

Draft Range: Mid-to-late lottery

He's cooled off during Barcelona's last couple of games, but for the most part, Mario Hezonja has packed a punch in limited playing time this season.

The Croatian wing is a supremely gifted athlete, shooter and creator, and he's putting those talents to good use across Europe. Hezonja is rising up and burying triples over anyone and everyone, and his slashing game burns foes who overcompensate on close-outs.

As a bonus, his passing game has noticeably improved. He's operating confidently and fluidly in pick-and-roll scenarios, averaging 3.6 assists per 40 minutes in ACB competition.

His defense won't really help or hurt his 2014-15 grade, as he's delivered mixed results. Rob Scott of Euroleague Adventures explained that Hezonja was disengaged early in the season but exerted more effort as the winter unfolded.

Hezonja's humble portion of playing time has hurt his chances to earn a sparkling assessment, yet it won't keep him out of the lottery. Scouts know he's fighting for minutes on an elite European squad, and his brightest days will likely come in the NBA.

Grade: B+

7. Willie Cauley-Stein, Kentucky C (7'0", Junior)

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2014-15 Stats: 25.4 MPG, 9.1 PPG, 6.4 RPG, 1.6 BPG, 60.3 FG%, 58.9 FT%, 24.5 PER

Impressive Game: 21 PTS, 12 REB, 3 BLK, 5 STL (Dec. 5 win vs. Texas)

Disappointing Game: 7 PTS, 13 REB, 5 TO (Jan. 6 win vs. Ole Miss)

Projected NBA Role: Rim protector

Draft Range: Mid-to-late lottery

Part of the reason Willie Cauley-Stein yields minimal offensive output for Kentucky is the prolific talent of his teammates. But two other big factors are his still-limited skill set and wavering confidence as a post player.

Coach John Calipari would like to see him be more adventurous with the ball.

"I want Willie to risk more. Risk! Go make a play!" he told Mike Bresnahan of the Los Angeles Times.

The bottom line is he's posting 9.1 points per game in his junior year, and he's getting to the free-throw line just 3.1 times per night. That means his NBA offense will be largely putbacks, assisted buckets and gift-wrapped opportunities.

High-octane defense is his calling card anyway.

He leads the SEC in defensive win shares (2.8) thanks to his ability to corral all players and force turnovers. Cauley-Stein rarely gives opponents a chance to shoot, and when they dare, it's almost never a clean look at the rim (click here for the latest ruthless evidence). If he can become a more physical rebounder, he'll be one of the absolute best center stoppers in the NBA.

Grade: B

6. Kristaps Porzingis, Latvia PF (7'0", 1995)

2014-15 Stats (ACB): 21.8 MPG, 10.1 PPG, 4.7 RPG, 46.6 FG%, 33.3 3PT%

2014-15 Stats (Eurocup): 20.7 MPG, 11.1 PPG, 4.2 RPG, 53.8 FG%, 42.4 3PT%

Impressive Game: 18 PTS, 7 REB, 4 AST, 4 STL (Oct. 29 loss at Virtus Roma)

Disappointing Game: 4 PTS, 4 REB, 1-of-5 FG (Dec. 21 loss vs. Morabanc Andorra)

Projected NBA Role: Stretch 4

Draft Range: Mid-lottery

Much of Kristaps Porzingis' draft value is based on noticeable potential for the future. However, he still earns a decent, if unspectacular, grade for his 2014-15 performances.

His slender frame and underwhelming rebounding are the two noteworthy concerns at this stage. Porzingis is averaging fewer than five rebounds per game in both ACB and Eurocup play, which is less than desirable given his length. As a post defender, he sporadically gets fooled or bullied, but in many cases, he holds his ground against sturdy foes.

As for the offense, it's tantalizingly promising. He's a 7-footer who's dangerous from any spot on the floor. Porzingis has made 33 percent of three-pointers in the ACB, and he's sizzling against Eurocup teams at 42 percent from the arc.

The young Latvian is also nimble and athletic enough to attack closeouts, and he can finish forcefully above the rim. He's not a master in the post, but his ball-handling ability and soft touch are readily apparent.

Grade: B+

5. Stanley Johnson, Arizona SF (6'7", Freshman)

Rick Scuteri/Associated Press

2014-15 Stats: 28.3 MPG, 14.1 PPG, 6.8 RPG, 44.9 FG%, 34.6 3PT%, 23.6 PER

Impressive Game: 20 PTS, 8 REB, 2 AST, 0 TO (Feb. 13 win at Washington)

Disappointing Game: 7 PTS, 3 REB, 0 AST, 4 PF (Jan. 11 loss at Oregon State)

Projected NBA Role: All-purpose swingman

Draft Range: Mid-to-early lottery

Arizona's star freshman, Stanley Johnson, is able to impact games in several areas, courtesy of his strength, motor and versatility.

His scoring production has fluctuated throughout the season. But when he's not busy scoring, he's putting his stamp on the offense by making plays for teammates and crashing the glass. He pulls down multiple offensive rebounds per game and is dishing 2.7 assists per 40 minutes in conference play.

Johnson has demonstrated encouraging effectiveness as a jump-shooter. He's hitting a modest 34.6 percent from long distance, and he's drilling 46.1 percent of his two-point jumpers, per Hoop-Math.com.

"Scouts repeatedly praise Johnson’s better than expected shooting," said Chris Mannix of Sports Illustrated. "…Several execs believe he has All-Star potential."

On defense, he's not perfect, but his physical dominance and instincts make him an upper-echelon asset. He plucks 1.5 steals per game and thrives on crashing the backboards.

Given the way he's influencing games for the Wildcats, it's impossible to give him anything lower than a B+.

Grade: B+

4. Emmanuel Mudiay, China PG (6'5", 1996)

Sam Forencich/Getty Images

2014-15 Stats: 30.0 MPG, 17.7 PPG, 5.9 APG, 49.7 FG%, 30.0 3PT%

Impressive Game: 22 PTS, 13 AST, 11 REB, 0 TO (Nov. 9 win vs. Qingdao)

Disappointing Game: 16 PTS, 9 AST, 7 TO, 7-of-15 FG (Nov. 12 win at Fujian)

Projected NBA Role: Attack-mode point guard

Draft Range: Top-five pick

Some college studs have leapfrogged Emmanuel Mudiay in various mocks and big boards, and that's fair because they have played more games against more quantifiable competition.

But don't sleep on Mudiay as a cream-of-the-crop prospect. Even during his small sample size of games in China (10 games), he flashed an electrifying skill set.

Against pretty much any opponent, he was able to speedily maneuver his way into the paint and wreak havoc. When it comes to slashing and making plays, he's more than ready to graduate the ranks of the CBA and start attacking NBA defenses.

"He has the burst to get by most players, and the angular instincts to hold defenders at bay once he turns the corner," said CBS Sports' Sam Vecenie. "Not only that, but [he] has excellent passing skill and vision to create. He's an elite player in this class."

He must work diligently to improve turnovers and shooting, however. Mudiay coughed up 3.1 turnovers per game in China, often via over-ambitious forays into traffic. Meanwhile, his jump shot and free-throw shooting are still inconsistent and flawed. He was just 9-of-30 from three-land, and he sank just 58.1 percent of his free throws.

Grade: B+

3. D'Angelo Russell, Ohio State PG (6'5", Freshman)

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2014-15 Stats: 33.2 MPG, 19.0 PPG, 5.3 APG, 46.1 FG%, 42.4 3PT%, 28.0 PER

Impressive Game: 22 PTS, 10 AST, 6 REB (Jan. 25 win at Indiana)

Disappointing Game: 13 PTS, 4 AST, 4-of-16 FG (Dec. 30 loss vs. Iowa)

Projected NBA Role: Dual-threat point guard

Draft Range: Top-three pick

With innovative court vision and a knack for splashing jumpers from anywhere, Ohio State's D'Angelo Russell has skyrocketed up draft charts during the past couple of months.

He has a natural feel for creating scoring opportunities, because he anticipates plays developing and puts his teammates in great position to score. Russell is not shy about generating his own buckets, however, as he can shake free for jump shots or drives throughout the game.

Consequently, most of his offensive statistics are exceedingly impressive for a freshman: 22.9 points and 6.4 assists per 40 minutes, 42.4 percent three-point shooting and 78 triples (most in the Big Ten).

The young Buckeye also rebounds superbly for his position, and he's an above-average defender when engaged. Russell has given us loads of evidence to suggest he'll be a dependable all-around guard early on in his NBA career.

His 2014-15 grade isn't pristine because he occasionally gets sloppy (3.4 turnovers per 40 minutes) and has defensive lapses. But given his playmaking brilliance and emergence as the Big Ten's top dog, he certainly deserves something in the "A" range.

Grade: A-

2. Karl-Anthony Towns, Kentucky PF/C (6'11", Freshman)

Andy Lyons/Getty Images

2014-15 Stats: 20.2 MPG, 9.3 PPG, 6.5 RPG, 2.3 BPG, 56.0 FG%, 79.8 FT%, 29.8 PER

Impressive Game: 19 PTS, 8 REB, 3 AST (Feb. 7 win at Florida)

Disappointing Game: 9 PTS, 9 REB, 5 PF, 5 TO (Jan. 10 win vs. Texas A&M)

Projected NBA Role: Stretch 4/Power 4 

Draft Range: Top-three pick

As Karl Towns' body of work grows and his versatility is increasingly evident, his argument for the No. 1 draft slot is picking up steam.

The Kentucky freshman is outclassing the Wildcats' challengers as if he were an upperclassman. His two-way impact is unstoppable for most opponents. He athletically gobbles up rebounds, sinks baby hooks and blocks shots in his sleep.

Towns' energy and length are game-changing, as he's among the SEC's top five in rebounding percentage, block percentage, defensive rating and defensive win shares. Despite a high foul rate (5.7 per 40 minutes), he's shown us plenty of proof he'll be a top-tier rim protector in the Association.

On offense, he's not as statistically dominant, but he's been extremely effective. 247Sports scout Jerry Meyer praised the youngster's multidimensional impact. 

"[Towns] can score over NBA length in the post and can stretch the floor with his shooting ability," Meyer said, per Chris Fisher of 247Sports. "He is an 'outside his area' rebounder and on top of all this, he is a proficient ball handler and tremendous passer."

Lottery suitors are licking their chops, because they know this is just the beginning. Towns' improvement, coordination and thirst for learning indicate a stellar ceiling.

Grade: A- 

1. Jahlil Okafor, Duke C (6'11", Freshman)

Grant Halverson/Getty Images

2014-15 Stats: 31.1 MPG, 18.2 PPG, 9.6 RPG, 66.3 FG%, 52.5 FT%, 31.6 PER

Impressive Game: 30 PTS, 9 REB, 13-of-18 FG (Feb. 25 win at Virginia Tech)

Disappointing Game: 14 PTS, 8 REB, 5-of-12 FG (Feb. 2 win vs. Georgia Tech)

Projected NBA Role: Featured low-post center

Draft Range: Top-three pick

If we were to grade Jahlil Okafor based on traditional stats or offensive production, he'd be pulling down an A or A+.

But a closer look at his defensive stats and game film reveals some holes.

Okafor's uninspiring interior stoppage isn't the only reason Mike Krzyzewski has opted to run zone more than ever before, but the two events are definitely related. The big man has trouble containing quicker opponents, and he gets burned off the dribble and in pick-and-rolls frequently. In conference play, his defensive rating is an uninspiring 101.6.

With the defensive shortcomings in mind, he remains a tremendous prospect due to his offensive value and size.

Most college players can't handle him in the post, and once he gets comfortable in the NBA, most pros won't be able to handle him either. Okafor is using his strength, footwork and scoring touch to convert 74.8 percent of his shots at the rim, per Hoop-Math.com. That's especially impressive because nearly half of his attempts are unassisted.

Factor in his passing abilities and solid rebounding tools, and you can see why he's viewed as a transformational low-post foundation for lottery-bound franchises.

Grade: A-

Note: Unless otherwise indicated, all stats come from Sports-Reference.com/CBB and are current entering March 2. All international stats come from RealGM.com.

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