RJ Barrett and Kevin Knox are more than just NBA teammates. They represent much of the hope and frustration that surrounds the New York Knicks team from a fanbase starving for a young nucleus to develop into a playoff contender.

But as Barrett and Knox navigate their way through expectations and the bright lights of New York City, there is something else often getting in their way: screeners. That pesky traffic on a midtown basketball court.

In fact, Barrett and Knox ranked first and fourth, respectively, for the percent of defensive possessions when they were the primary defender against a shooter coming off a screen this past season (minimum 50 possessions), per Synergy tracking data.

There are a few obvious reasons why a defender might find themselves battling through obstacles to defend their man: first, position and matchups matter; and second, opposing teams might target said player.

But in examining why Knox and Barrett have been put into so many screen situations, a third reason becomes apparent: when your defense is inexperienced and lacking, opposing teams might try to put you in thinking situations that require switches and rotations that you are unlikely to execute. The play below is a perfect example of this:

Indiana has a lot going on under the basket. Notice how Damyean Dotson winds up facing the wrong direction as his man starts to sneak under the basket to curl toward the 3-point line for a catch-and-shoot opportunity. Knox switches off his man — McDermott — once Dotson has turned the right way, but gets picked. This is a difficult play to defend, but when you’re a step slow and a bit confused, you have no chance.

The Knicks saw the greatest percentage of off-screen movement from opposing offenses in the NBA this past season, per Synergy. Both Knox and Barrett, two players who oftentimes were required to defend an opposing shooter, saw their individual totals against screens inflated as a consequence.

Knox struggled in these situations, allowing 1.25 points per possession, seventh-worst among defenders who saw at least 50 off-screen defensive plays. Anyone who has watched the Kentucky product pull at his shorts on defense could have guessed the numbers would match the eye test in his ability to follow social distancing protocols in defending his man, but in watching the corresponding film to explain the statistics, there is a bigger problem at play.

In the video below, we see Knox a step slow in reacting to a moving Doug McDermott. OK, fine. But in watching the clip, focus on Mike Miller at the top of the frame. He appears to grow upset around the time Knox gets caught on the high screen. Mitchell Robinson is hovering around the foul line at this point, giving McDermott plenty of space to launch a three. Just one step too deep keeps even the longest of arms from properly contesting the shot. This outcome counts against Knox’s defensive metrics, but if Mitch was positioned better — literally a step closer, which still gives him space to respect the drive — perhaps McDermott would have been stopped.

It turns out teammates matter when trying to play good defense. You can be an excellent individual defender, but on plays that require movement and rotations, you need help. It’s ironic to isolate Mitch in the play above, as he is one of the team’s stronger defenders in terms of protecting the rim. But he still has work to do in the finer details of his game.

For Knox, he most often shared the floor with Dotson and Frank Ntilikina as his backcourt mates, two players who are more than capable of handling their own on the defensive end — or, more importantly, providing help when needed. Interestingly, the Knicks were a net positive team when Knox was on the floor with either of those defenders. They were negatively rated when Knox shared the floor with any of the eight other teammates he played at least 150 minutes with last season.

RJ Barrett is a different story. Playing mostly as a two-guard, or with three definitive forwards on the court at the same time, he saw most of his time with either Elfrid Payton or Ntilikina in the backcourt, and almost never with multiple strong guard/wing defenders.

Yet, despite his high frequency in defending shooters on the move, the results were far better than when Knox was in the same situation. Of 64 defenders who saw at least 50 off-screen possessions, Barrett ranked 10th-best, holding opponents to just 0.818 points per possession, per Synergy Sports. 

So let’s review: Knox played more minutes with teammates who are better equipped to help on defense against shooters on the move than Barrett, but Barrett’s tracking data shows he was more effective in stopping shooters from scoring.

The eye test tells us Barrett is about as good at avoiding screens as my 5-year-old during this pandemic. So what gives?

This is where we enter into the messy territory of trusting defensive metrics. Understanding how a player performs on defense requires knowledge of their assignment (oftentimes unknown to the public), and review of film to decipher where players are receiving credit (or blame) for their defense.

As an example, we have the play below:

As you can see in the video clip, Barrett is defending Doug McDermott off the screen, but there appears to be a miscommunication on the switch with Elfrid Payton. This is an example of how it is challenging to associate individual statistics to defensive outcomes. McDermott misses the shot, Barrett was the primary defender, so he gets “credit” for this play turning into 0 points. However, it’s unclear who is to blame for the miscommunication on the switch. Was Barrett supposed to switch here, or not?

A clear example of Barrett showing his ability to defend off the screen comes on this play:

Screened on a sideline out-of-bounds play, Barrett uses an efficient route and sound mechanics (notice his left arm is in a blocking position for several steps) to keep Kemba Walker from gaining an edge, and eventually blocks the shot. Notice, too, that Barrett is defending a point guard on this play — which he did a fair amount of times in his rookie season. This is more than just fighting through a screen; it’s staying on the play after the pick.

It turns out that when RJ defends a player off the screen who is more prone to continue the play with their dribble — again, think point guards — he does fairly well. He can use his size and quickness to recover, rather than counting on his teammates to switch and help. However, when he’s a step slow or unable to take an efficient route around a screen against a pure shooter, the results aren’t as good — something that the tracking data isn’t perfect in separating out.

Broadening our focus away from just screen plays, Kemba, De’Aaron Fox and Kyrie Irving shot a combined 5-15 (33%) when Barrett was the primary defender this year. Of course, there are examples of matchups against point guards where the numbers aren’t quite as good — James Harden shot 5-6 against him — but there are promising signs that Barrett can work as a defender off the dribble, away from the action that starts under the basket and ends with a shooter four steps ahead of him draining a three.

What does all of this mean? Analyzing defense is complicated. We don’t know all of the answers. We watch the games to get an idea of how a player performs. Statistics become good descriptors. Re-watching the film helps us level-set our initial conclusions. And sometimes the individual trends we see are a product of something bigger.

The Knicks don’t just need Kevin Knox and RJ Barrett to become a step quicker in keeping with their opponents on defense (and enough confirmation tells us Knox needs to more than RJ); they need new coach Tom Thibodeau to instill a defensive scheme that allows all five players on the court to work as a unit. We saw the example above with Mitchell Robinson: every step counts. Hopefully, Thibs helps them get there.