Here's why the Knicks' defense has collapsed, and what they can do to fix it

This Knicks era can be defined by many things, but one undeniable core tenet has to be their defense under head coach Tom Thibodeau. He made his name on that end of the court, and brought the same full effort, full intensity philosophy to a New York franchise desperately needing it.

The results are hard to complain about. The Knicks had the fourth-best defense and a fourth seed finish in 2021, and the second-best postseason defense and a second-round trip in 2023.

This season looked like another strong campaign through Dec. 2, as they allowed 109 points per 100 possessions, good for fifth in the league. However, that’s since changed drastically, as the Knicks had the worst defense in NBA over their next six games, giving up a whopping 131.3 points per 100 possessions.

What changed in that time, and what can the Knicks do to fix it?

The biggest changes in that stretch have come to the starting lineup, both by choice and chance. Quentin Grimes was replaced by Donte DiVincenzo in the opening unit after complaining about his limited role, and Mitchell Robinson went down with an injury.

These switches have steadily disintegrated whatever defensive tenacity the starters had to begin the season. The original five of Jalen Brunson, Grimes, RJ Barrett, Julius Randle and Robinson allowed 104.8 points per 100 possessions, which would rank first in the league, in 228 minutes.

The DiVincenzo swap bumped that number up to 144.6. Once Jericho Sims took Robinson’s spot, it remained a porous 139.7. It’s no surprise as to why.

Grimes is the team’s best perimeter defender, taking the toughest assignment every night and rarely looking out of his depth. He’s had strong individual nights against Damian Lillard, Paul George and other stars, and will guard anybody 1-3.

DiVincenzo brings a different defensive energy, less conservative and more coming to take your ball away. He can be a spark on that end but isn’t nearly up to the reliability of Grimes, whose minutes have dropped from 22.9 to 18.7 since the benching.

This is reflected in their individual defensive ratings, where Grimes has a 111.4 and DiVincenzo a team-worst 119.3. This isn’t too say the drop off is entirely on DiVincenzo or that he’s a bad defender, only that it’s a factor.

Meanwhile, Robinson was having a career year, his best defensive campaign with a real bid for All-Defensive First Team. He seemed to fully grasp his role and positioning on every possible play, and matured to the point of hardly chasing blocks over the well-timed contest and board.

In trying to maintain his potent bench unit and current rotation pattern, Thibs went with Sims over the natural backup Isaiah Hartenstein, like he did when Robinson went down last year. Unfortunately it hasn’t worked as well.

Sims still looks raw and jumpy, and while he’s had some moments, isn’t ready to start.. Hartenstein has looked good in his minutes, and pushing him into the starting lineup seemed like an easy way to stop the bleeding somewhat.

Now that Sims is hurt, Hartenstein will get that chance, but the Knicks will have a hole to fill behind him. It will come down to veteran Taj Gibson and whatever small lineups New York runs between Randle or Josh Hart at the five.

While it’s easy to pin the decline on those two specific rotation changes, there’s definitely more involved. Some seasonal regression and loss of effort is always due, and as evidenced by the Lakers and Nets wins, the Knicks can quickly turn it back up.

Opponent three-point shooting luck is also a factor. They hit 35.6 percent of their threes in the opening stretch, which increased to a scalding 42.7 percent in those six games, on the same frequency of open looks.

That number will even out eventually, and the Knicks should see a surge defensively. These last two outings have already been much better, and it’s likely the team will be active in the trade market looking for upgrades.

The Knicks are in the thick of an Eastern Conference playoff race with a few other teams hovering over .500, but if they want to separate themselves they’ll have to recommit to defensive culture.