Here's an old breakdown I did for Nerlens over the summer broken up into 3 parts and edited. I'm not saying what I'm seeing is fact, but I just want to point out some strengths and weaknesses that I want to see improvement on. Then we can really see if Nerlens is regressing or improving going into his contract year.

Let’s start with his bread and butter. There’s no need bring up stats that have been thrown around again and again, but it’s clear Nerlens is capable of anchoring a top NBA defense. Even while surrounded by below-average perimeter players, and paired with unfavorable front court partners.

His blocks and rim protection need no breakdown, it’s clear he can be an elite force there. What’s more interesting is how he blocks shots. Too often shot blockers try to swat the ball out of play, but it’s much more practical to keep the ball in play for yourself or a teammate to rebound:

Nerlens shows excellent control and is able to block shots while keeping them in play. Unfortunately, sometimes they end up in the hands of an opponent, but sometimes they can result in transition opportunities:

He also can send the ball out of play when there’s no teammate to recover and/or it’s time to send a message:

Like most shot blockers, he has a bad habit of jumping the gun and ending up in the air before the shot is taken and giving up an easy basket to his man:

Being an active jumper is good for intimidation, but without another shot blocker it’s unwise to go in the air so frivolously. Here’s a good example of Nerlens staying disciplined and remaining on the ground to contest and rebound:

That intimidation doesn't just show up around the rim. It allows Nerlens to affect shots or stop actions without actually contesting shots. Some examples are causing guys to lose handle or make a bad pass when they see him go to the rim, or prevent back doors and hand offs:

A unique aspect of his defensive game is his ability to steal the ball. Opponents with weak handles or who are weak with the ball are easy prey for Noel’s poke steals due to his insanely quick hands:

Sometimes he will swipe at the ball instead of moving his feet to stay in front or recover:

Needs to stay away from this unless there is another rim protector in the paint. Has shown the ability to stay with guards, small forwards, and quicker power forwards using his foot speed.

He’s also great at anticipation steals (and has been much better at finishing them in transition after his Shaqtin a Fool moment early in the season):

He also deflects passes at a high rate. With his quick hands and length it’s hard to get basketballs around him:

This picture above was actually called a kick ball. I don’t fault the ref, it took me a long time to pause the video at the right time to get that screen grab. His hands are sometimes too quick for real time.

Even more so than his rim protection, Nerlens’ best defensive ability is his prowess on the pick and roll. With his quick feet, hands, length, and shot blocking ability he is a menace as a pick and roll defender and is capable of all types of pick and roll defense:

His long arms allows him to sag off of players, and still affect shots and get deflections with his length. This is best used when switched onto guards who can shoot and drive, as it gives Nerlens space to move his feet if they attack:

There are some aspects of defense he needs to improve on. His closeouts at times can leave a lot to be desired. Even though a lazy closeout with his length is still enough to contest a shot, better and/or taller shooters will still make their shots:

However, has shown that with good effort can have impressive closeouts inside the arc:

And outside the arc:

Needs to consistently give max effort on closeouts, especially if he is going to be patrolling the paint while his man is on the perimeter.

I’ve seen a lot of false narratives about Noel’s 1 on 1 defense like "he’s below average" or "any physical center can abuse him". That’s incorrect. Nerlens has shown that he is more than capable of defending centers 1 on 1:

Noel’s true Achilles’ heel isn’t physical centers, but skilled ones. The obvious example from this year is Nikola Vucevic. His combination of low post moves and shooting gives Noel problems:

Good offensive centers are going to be able to get their shot off. In the clip above you see Noel contesting the shots well, but hooks and floaters are mostly unblockable and a good big can get it off regardless of defense. What Noel must do is to play physical instead of his usual technical style of defense:

As you can see, even a little bit of contact can throw off a hook/floater. Noel will need to get stronger to be able to bang consistently with guys like that.

Vucevic’s ability to put it on the floor makes Noel reluctant at times to close out on his shot, which accentuates one of his defensive weaknesses:

Noel is also guilty of the occasional mental lapse defensively:

And his transition D hasn’t been as devastating as it once was since his ACL injury, sometimes reluctant to go full speed or elevate to get the chase down block:

Still, when committed can be a force in transition defense:

When engaged he can take over possessions defensively taking on multiple defensive assignments:

I see a lot about how Noel isn’t unique and can be replaced, but how many players, let alone bigs, can recognize the mismatch on the right wing, go double, then beat the pass to the left wing and poke way the ball away like he did in that GSW clip?

So while he is not a perfect defender, most of his issues can be corrected with more disciplined technique, increased strength and IQ, and improvement on what he’s already good at. These are all things that should progress naturally with age and experience. His true defensive impact won’t show up on any metric available to the public. If he does continue to progress, there’s no doubt in my mind DPOY honors are in his future.