NBA’s Top 25-and-Under Defensive Weapons

by Daniel O'Brien

While the NBA is littered with young offensive standouts, high-level defenders aren’t quite as abundant.

It’s exceptionally difficult to shine defensively in today’s league. Scorers and playmakers are more skilled than ever while officiating lends itself toward a high-scoring brand of hoops.

Nonetheless, I’m assessing the top young defensive weapons in the second part of my series on the NBA’s 25-and-under talent. I’m examining everything from one-on-one defensive talent, team defense aptitude and defensive rebounding effectiveness.

My rankings are based on a mix of the eye test and advanced metrics like NBA Math’s Defensive Points Saved, Basketball Reference’s Defensive Box Plus/Minus and NBA.com’s defensive tracking tools. I also factored in the context of each candidate’s team situation and environment. After all, not every player is put in an optimal position to excel defensively.

Honorable Mentions: Matisse Thybulle (PHI), Mitchell Robinson (NYK), OG Anunoby (TOR), Jayson Tatum (BOS), Domantas Sabonis (IND), Jakob Poltl (SAS), Nerlens Noel (OKC)

5. JONATHAN ISAAC, ORLANDO MAGIC F (22.4 YEARS OLD, 3RD SEASON)

Key Defensive Stats: 5.0 Defensive Box Plus/Minus (DBPM), 96.7 Defensive Points Saved (DPS), 2.0 Defensive Win Shares (DWS), 42.5 Defensive Field Goal Percentage (DFG), 19.2 Defensive Rebounding Percentage (DRB)

Isaac has been on the shelf for a month-plus with a knee injury, but his pre-malady impact warranted recognition. He owns some of the best defensive tools of any young player, and Orlando has struggled on that end without him.

Coming out of Florida State three years ago, scouts had hoped the 6’11” forward would blossom into a defensive standout. Isaac has gradually lived up to the expectations, pairing his towering frame with uncommon nimbleness and instincts. Playing in Steve Clifford’s disciplined system has undoubtedly been beneficial for him as well.

Isaac has outstanding alertness and timing to jump passing lanes, and his long arms do the rest of the work. Opponents have fired countless ill-advised passes that he’s picked off or deflected, turning them into easy points on the other end:

Plays like that are commonplace for Isaac. He has the luxury of sitting back, camouflaging as a helper or lane-clogger, fooling the passer into thinking the receiver is open.

Then he darts into the passing lane and looks like a varsity player toying with the JV squad.

If the Magic ever put together a truly dangerous team, Isaac’s defense will be a crucial weapon in the playoffs. It’s exciting envisioning him squaring up with the likes of Giannis Antetokounmpo, Pascal Siakam and Jayson Tatum during meaningful games.

4. Jarrett Allen, Brooklyn Nets C (21.8 years old, 3rd Season)

Key Defensive Stats: 3.3 DBPM, 98.4 DPS, 2.5 DWS, 44.5% DFG, 24.7% DRB

Most defenders concede thunderous dunks to the league’s best slashers because it’s a fool’s errand trying to stop them. It regularly ends with posterization or a foul.

But Allen is one of the few defenders with the tools, talent and fortitude to challenge anyone above the rim. He went viral in 2018-19 on several occasions by rejecting a slew of superstars:

This season, he’s become an even better interior defender, improving key components like his footwork, post strength and defensive rebounding. Allen is sturdier and stronger when battling for rebounds or low-post defensive positioning.

Logan Gilchrist of The Brooklyn Game noted Allen’s increased power in the paint:

The biggest question mark for Allen coming into this season was his size and toughness…it is clear that he has improved. The Fro is now able to hold his own against centers that once dominated him physically. His presence on the boards…was one of the deciding factors in the Nets snapping the Raptors’ streak.

Allen is grabbing 11.7 defensive rebounds per 100 possessions and posting a defensive rebounding percentage of 24.7, both career-high marks. As he continues to improve his balance between disciplined positioning and assertive shot contests, his bottom-line value in Brooklyn will skyrocket.

3. Bam Adebayo, Miami Heat F (22.6 years old, 3rd Season)

Key Defensive Stats: 4.0 DBPM, 152.2 DPS, 3.0 DWS, 43.9% DFG, 24.2% DRB

Miami’s breakout star has had just as much success on defense as offense, if not more. Adebayo’s value lies in his lateral and vertical explosiveness, as well as his outstanding timing and instincts.

Even though he’s not as tall as most bigs—he’s 6’9” with shoes on—he gets off the floor so quickly that it doesn’t matter. He routinely beats opponents to the summit, forcing them to put up awkward shots or get blocked. Foes are shooting  57.5 within six feet of the hoop against Adebayo, which is 4.2 percent below their average against the rest of the league.

He has a sharp sense for steering opponents away from their sweet spots. In this sequence against Giannis Antetokounmpo, Adebayo denies a right-handed drive without yielding too much on the baseline. He finishes the play with a great contest:

Adebayo’s nearly equally adept away from the basket.

He has quick hands to pluck steals from ball-handlers or passers, and he challenges shooters better than most swingman defenders. He’s averaging 1.8 steals per 36 minutes, and three-point shooters are converting just 32.7 percent against him. He has a great feel for when to help and recover versus when to just stay home. Those kinds of decisions aren’t easy for most third-year players.

Adebayo also has a special knack for intercepting alley-oop attempts, displaying terrific timing and athleticism to detonate potential highlight plays:

2. Ben Simmons, Philadelphia 76ers F (23.6 years old, 3rd Season)

Key Defensive Stats: 3.3 DBPM, 131.4 DPS, 3.4 DWS, 41.3% DFG, 17.8% DRB

Few players of any age can bottle up the NBA’s biggest offensive stars better than Simmons. Philly’s point-forward is a model of defensive versatility, with the tools to check almost every type of player.

He can pull this off because he has unbelievable agility for a 6’10” forward. Simmons can challenge shifty guards on the perimeter and stay in front most of the time. And even when they shake past him with a great move, he takes terrific recovery angles and uses his size to minimize the damage.

In addition to providing rangy containment against drivers, Simmons serves as a stout interior defender and a timely thief in passing lanes. Tom West of Liberty Ballers shared this montage of Simmons’ defense against the Indiana Pacers, showcasing the star’s disruptiveness and versatility:

Simmons’ ability to guard positions 1 through 5 offers terrific schematic flexibility. Sometimes coach Brett Brown assigns Simmons to the opponents’ top ball-handler and playmaker, and other times he puts Ben on the opponents’ top rim diver.

During any given possession, Simmons can switch onto anyone and derail the whole thing.

1. Giannis Antetokounmpo, Milwaukee Bucks F (25.2 years old, 7th Season)

Key Defensive Stats: 5.1 DBPM, 165.7 DPS, 3.9 DWS, 36.9% DFG, 32.9% DRB

Among all players with at least 30 games played, Antetokounmpo leads the league in Defensive Field-Goal Percentage, Defensive Points Saved, and Defensive Win Shares. So not only is he the top defender among the 25-and-under crowd, there’s a solid argument that he’s the top stopper on the planet.

He fortifies Milwaukee’s team defense, particularly on the interior, because he’s a monstrous help defender. Everyone knows about his ridiculous wingspan and athleticism, yet slashers and rim-divers still underestimate his knack for flying in from the weak side.

Just when would-be scorers think they beat their man and have room for a bucket, Antetokounmpo snuffs out their chance or alters their shot. Even Anthony Davis in the All-Star game isn’t safe from Giannis’ reach:

It’s not all about Antetokounmpo’s length, though. It’s also about his length plus his effort.

Whether it’s his vigilance on the defensive glass, fighting through screens or jockeying for position, Antetokounmpo’s motor puts him in a position to succeed.

In the following sequence, his energy trumps the Magic’s attempt to free Aaron Gordon. Giannis darts in front of the inside ball screen, and when Nikola Vucevic wisely flips the screen, Antetokounmpo fights to get through and stymie Gordon:

Antetokounmpo’s defense gave him the edge in the 2019 NBA MVP race, and he’s only improved upon it in his quest for another MVP trophy. There may be more talented and shrewd defenders than him throughout NBA history, but no one has ever had his combination of length, agility and energy.

It’s been amazing to watch him ascend to an elite level on the less-heralded end of the court.

Unless otherwise noted, all stats gathered from NBA.com and Basketball-Reference.com. Stats are updated as of February 20, 2020.