Exposing the NBA's Worst Defenders
Even in sports' age of information, analyzing NBA defense remains a largely subjective endeavor.
On the other end of the court, points, assists, efficiency and impact aren't difficult to quantify. On defense, things like communication, helping, nailing rotations and boxing out don't make it into the box score.
We have impact and catch-all metrics like box plus/minus, RAPTOR rating, net rating swing and more that at least try to ballpark a player's effectiveness on that end, but even those have to be taken with grains of salt.
"Box Plus/Minus is good at measuring offense and solid overall, but the defensive numbers in particular should not be considered definitive," Daniel Myers wrote for Basketball Reference. "Look at the defensive values as a guide, but don't hesitate to discount them when a player is well known as a good or bad defender."
The most glaring example of this may be Golden State Warriors defensive ace Klay Thompson, who has posted a below-average defensive box plus/minus in every season of his career, despite often guarding the opposition's best perimeter player and generally having a positive impact on the team's overall defense.
FiveThirtyEight's RAPTOR rating tries to incorporate more information into its catch-all, including things like on-off splits and individual play-type data, but it too is fallible.
What does all this mean? It's fun to look at defensive numbers, and as Myers instructs, use them as a guide, but a real grasp of NBA defense can only be achieved by watching defensive possessions.
That, the aforementioned numbers and a healthy dose of subjectivity is what went into the selection of the following players. But first, a few more disclaimers.
Rookies were not considered for this exercise. It takes time to learn how to defend at this level, and this particular rookie class was robbed of summer league and a typical training camp. Someone like Killian Hayes has horrendous defensive numbers. They may stay that way, but it's way too early to make that call.
A few youngsters are also getting the benefit of the doubt with early 2020-21 returns. Had this topic been explored before the start of the season, Collin Sexton and Trae Young likely would've been prime candidates. Both seem to be making positive strides, though. Their teams' defenses are better with them on the floor. Young is actually holding opponents below their expected field-goal percentage. And they both look more aware on defense.
Those on the following list have demonstrated no such progress in 2020-21. On top of poor defensive marks in the seasons leading up to this one, they're struggling to contain opponents.
2020-21 Defensive RAPTOR Rating: Minus-3.6
2020-21 Defensive Field-Goal Percentage: 54.9 (compared to 48.7 expected)
Defensive Box Plus/Minus since 2018-19: Minus-1.1
Career Net Rating Swing: Minus-3.5
Enes Kanter is an offensive juggernaut. No, really. During his career, he's averaged 20.1 points and 5.1 offensive rebounds per 75 possessions, numbers matched only by the legendary Moses Malone. But he gives all of it back (and then some) on defense.
During his 10 NBA seasons, his teams are minus-2.5 points per 100 possessions with him on the floor and plus-1.0 with him off. And in 2020-21, he's on track for an eighth straight year in which his team allows more points per 100 possessions with him on the floor.
Reasons for the lack of a positive impact on defense are varied. For one, he's not the most fleet-footed big, and teams are quick to throw him into pick-and-roll coverage for that reason. When he tries to fight over the screen or hedges, guards are generally able to dribble right around him. Effective drop coverage would require elite perimeter defenders, which Kanter can't control, but opposing bigs often lose him there too.
Some centers find themselves out of position but still have the athleticism to quickly close gaps and contest shots. That's typically not the case with Kanter.
If he has a strength on that end, it's likely his ability to gobble up rebounds (8.2 defensive boards per 75 possessions for his career), but that's not enough to make up for his lack of mobility and awareness.
Glenn Robinson III
2020-21 Defensive RAPTOR Rating: Minus-7.1
2020-21 Defensive Field-Goal Percentage: 52.6 (compared to 44.5 expected)
Defensive Box Plus/Minus since 2018-19: Minus-1.1
Career Net Rating Swing: Minus-4.0
Glenn Robinson III may deserve the benefit of the doubt more than Young and Sexton. Unlike those two, he'd be receiving it for his track record, not early-season returns in 2020-21.
Over the first four seasons of Robinson's career, defensive box plus/minus pegged him as exactly average, which is no small feat for a wing (the metric tends to be kinder to big men who pile up defensive rebounds).
Things have been trending downward for Robinson since then, and this season has started disastrously. Only one player in the league has at least 100 minutes and a worse defensive RAPTOR rating (more on him later). And when Robinson is on the floor, the Sacramento Kings are allowing an unfathomable 129.8 points per 100 possessions.
Prior to 2020-21, the highest mark on record for a team was 117.6. These Kings are on track to be over two points worse than that. And they're over 10 points worse with Robinson on the floor.
Beyond the impact numbers, Robinson's level of activity on the defensive end has fallen off a cliff. Over his first six seasons, he averaged 1.1 steals and 0.4 blocks per 75 possessions. This season, he has zero steals and one block in 233 minutes.
That may partially be a product of scheme (the Kings are 27th in steals per 100 possessions this season), but those numbers and the eye test clearly show a step back in defensive intensity.
Marvin Bagley III
2020-21 Defensive RAPTOR Rating: Minus-4.7
2020-21 Defensive Field-Goal Percentage: 58.6 (compared to 47.3 expected)
Defensive Box Plus/Minus since 2018-19: Minus-1.8
Career Net Rating Swing: Minus-5.1
Some thought was given to barring the inclusion of two players from the same team, but Sacramento's historically bad defense steamrolled that consideration.
This season, Marvin Bagley III has shared the floor with Robinson for just 71 minutes (roughly a game-and-a-half). The Kings have given up a whopping 215 points and are minus-73 in those minutes.
Of course, that stretch is only about a sixth of Bagley's total minutes this season, and the rest of his time on the floor didn't save him from inclusion on this list.
Defense has been a problem for Bagley throughout his career, and basic numbers don't necessarily reflect that. He's posted decent rates for blocks and defensive rebounds, but those feel like the "well, someone has to collect these" sort of numbers we often see on bad teams.
When you watch Bagley play, he regularly misses rotations, gets caught napping off the ball and provides little resistance when an offensive player faces up on him.
As with Kanter, positives exist in Bagley's game, but they're almost exclusively on offense.
2020-21 Defensive RAPTOR Rating: Minus-7.8
2020-21 Defensive Field-Goal Percentage: 51.9 (compared to 44.6 expected)
Defensive Box Plus/Minus since 2018-19: Minus-2.1
Career Net Rating Swing: Minus-14.1
With CJ McCollum out for the foreseeable future because of a fractured left foot, third-year guard Anfernee Simons' defense (or lack of defense) is about to go under the microscope.
For his career, the Blazers have allowed 118.4 points per 100 possessions with Simons on the floor, and that mark doesn't get much better when he plays with Damian Lillard (a duo that has logged nearly half its total minutes together in the three games since McCollum left the lineup).
Because he's spent a significant chunk of his minutes on the wing, the 6'3" guard is often undersized defensively, something Bleacher Report's Jonathan Wasserman expected to haunt Simons.
"Simons will likely struggle defending NBA guards in his first few years, mostly due to his underdeveloped frame and limited experience," Wasserman wrote shortly after Simons was drafted in June 2018. "Long term, he has potential stemming from his quickness and length. He'll likely have more success defending point guards."
The optimism on his potential may still prove warranted. Simons is still a few months shy of his 22nd birthday. But that quickness and length has yet to be focused into positive defensive contributions.
Like Bagley, he often gets lost or caught napping off the ball. He struggles to stay in front of assignments on the perimeter, and when he does, many can just rise up and shoot over the top of him.
There's still a world in which Simons develops into an average or above-average perimeter defender, it's just a few parsecs away.
2020-21 Defensive RAPTOR Rating: Minus-3.3
2020-21 Defensive Field-Goal Percentage: 47.5 (compared to 45.8 expected)
Defensive Box Plus/Minus since 2018-19: Minus-0.1
Career Net Rating Swing: Minus-3.0
DeMar DeRozan is one of just 49 players in the three-point era with a career scoring average of at least 20.0 points. In his three seasons with the San Antonio Spurs, he's become a bona fide distributor, with an average of 6.0 assists per game. His mid-range prowess has helped to make him a positive offensive contributor in five of his last six seasons and is a welcome deviation from a league that is becoming increasingly homogeneous on that end of the floor.
But there's a reason DeRozan's teams have been better overall with him off the floor in 11 of his 12 campaigns. And it's the same reason San Antonio's plus-minus falls off a cliff when he plays this season.
In 2020-21, the Spurs are allowing 116.0 points per 100 possessions when DeRozan plays and 98.1 when he sits. Only three players in the league have played at least 100 minutes and have a swing that's worse.
Like everyone else on this list, there isn't any one thing we can point to and say: "See! That's why he's a bad defender." Instead, it's the combination of plenty of lapses.
Screens often stop DeRozan dead in his tracks. He sometimes seems like he can't be bothered with his assignment's off-ball movement. And he's often dusted in one-on-one coverage.
There's no question the four-time All-Star is a great offensive player, but he's gone from liability to borderline disaster on the other end.