Lynne Sladky/Associated Press

On New Year’s Day, Mike Dunleavy Jr. of the Chicago Bulls injured his foot in a game against the Denver Nuggets. Neither the severity of his injury nor the impact of his pending loss were immediately apparent. What’s happened since then, though, has made it obvious just how much he means to the Windy City.

Anyone who has ever built a model airplane knows the importance of glue: You don’t see it, but it’s the substance that holds all the pieces together. And when you’re putting the plane together, there’s always the ones labeled “A” and “B,” which are the big parts that form the body of the airplane. Those are like the stars, like Derrick Rose and Jimmy Butler.

Then there are the smaller pieces, like the parts that make up the tail or the wings. Those are the other significant players who may not be All-Stars but are still major components of winning—players like Taj Gibson.

But then there’s the substance that holds it all together and remains completely invisible—the glue guy. These aren’t the guys who fill up the stat sheet. The glue guys are just there to hold everything else together.

When you’re building your model, the goal is to keep the glue hidden. You don’t want big globs spilling over and ruining the aesthetic. And thus is the fate of the glue guy. In a way, you don’t even want to “see” him. That’s not his role.

But here’s the other thing about glue guys: You don’t know their importance until they’re out and everything starts to fall apart. Consider some of these splits for the Bulls, before and after Dunleavy’s injury, per NBA.com/stats:

Difference in Bulls Before and After Mike Dunleavy's Injury Category Before After Difference Offensive Rating 106.2 102.7 3.5 Defensive Rating 101.5 104.3 -2.8 Net Rating 4.7 -1.6 6.3 Effective Field-Goal Percentage 49.8 46.6 3.2 Field-Goal Percentage in Paint, Restricted Area 57.3 52.0 5.3 Field-Goal Percentage in the Paint, Non-Restricted Area 41.8 38.0 3.8 Points off Turnovers 14.5 13.1 1.4 Fast-Break Points 12.3 10.6 1.7 Opponents Points in the Paint 41.2 45.6 -4.4 Opponents Points off Turnovers 15.1 16.1 -1.0 NBA.com/Stats

Things are in disarray, and a lot of that has to do with Dunleavy’s absence. It’s not that his 9.6 points and 3.8 rebounds aren’t missed at all, but to judge him exclusively by those fairly pedestrian numbers is to vastly underestimate his significance.

Bleacher Report’s John Wilmes was prescient when he said earlier this year:

If Dunleavy ever gets injured and misses time for the Bulls—an experience that seems like a rite of passage for his squad these days—these qualities may finally be noticed when they’re absent. But since his play is always there, we seem to take it for granted as he blends seamlessly into the experience of enjoying winning Bulls basketball.

Here are some of his qualities, along with examples of each.

Help Defense

One of the glaring weaknesses in the Bulls defense since Dunleavy went down is that Pau Gasol just doesn’t have the foot speed to keep up with the quicker bigs or close out on those who have a little range. Nikola Vucevic of the Orlando Magic lit up the Bulls for 33 on Jan. 12. Jordan Hill of the Los Angeles exposed them with 26 on Jan. 29. Al Horford made 11 of 14 attempts on Jan. 17.

Vantage Sports tracks games in incredible detail, including“Points Against per Shot,” which is how many points an opponent scores when a player is defending the attempt. Prior to Dunleavy’s injury, Gasol’s Points Against per Shot was .89—seventh best out of the 50 power forwards with the most shots defended. But since then he’s giving up 1.02, which is only 36th.

That’s not just a coincidence either. Dunleavy’s help defense has a particular effect. He’s a long 6’9”, and because of that he’s been able to help Gasol in ways the other Bulls’ wings haven’t been able to. Dunleavy’s double-teams crowd the shooter and typically force a bad (and missed) look. Such was the case when the Brooklyn Nets’ Mason Plumlee found himself with nowhere to go, so he had to dump it out to Brook Lopez for an errant shot:

He’s also able to keep power forwards from getting the ball in the first place. This play is designed to go to LaMarcus Aldridge, but Dunleavy absolutely blankets him, denying any chance for the pass:

Since Dunleavy has been out, teams have gone after Gasol because it works. Before Dunleavy was out, he was defending 21.9 shots per game. Since then, he’s defended 23.7—the most of any player in the league.

Opponents are scoring 4.4 more points in the paint in the games Dunleavy has missed. At least some of those could have been prevented with his help defense.

Disruptive Defense

Similarly, Dunleavy’s is not a lockdown one-on-one defender who is going to stay in front of Kyrie Irving and shut him down, but he’s a very disruptive team defender. And that has value.

If I could coin and measure a term on the defensive end, it would be “defensive radius.” Having length and using length are not the same thing. Dunleavy is always using his full wingspan. His arms are either out by his side to disrupt passes or over his head when he’s guarding a shot. He plays with “radius.”

Per NBASavant.com, Dunleavy is 30th in the NBA in field-goal percentage against when he’s within three feet of the shooter. That’s in large part because he consistently has his hands up when guarding a shot.

But he also has his arms out. Here’s an example of him using his length to reach in and disrupt the dribble of the unsuspecting Shawne Williams of the Miami Heat.

That’s not the totality of Dunleavy’s disruptive defense. He can come out to the perimeter and muck up a play before it even gets started by pestering the ball-handler as he does here:

In addition to his length, he has no qualms about stepping in and taking a charge. Last year he was fourth in the league in charges taken with 20, per HoopsManifesto.com. This year he had four more before he was hurt. Typically, when he draws one, he saves points. For example:

None of these things happen every play, and I’m not going to argue that Dunleavy is the Defensive Player of the Year. But his team defense is bold, smart and disruptive, and that has an impact.

It usually results in one or two turnovers, which explains why the Bulls have averaged 1.4 more points off turnovers and 1.7 more fast-break points in games he’s played. And it usually saves a basket or two. That can make the difference between a win and a loss.

Spacing

“Spacing” is the trendy thing in offenses nowadays. “He stretches the court” is how a player who provides “gravity” is often described. What all that means in the simplest terms is a guy who is so lethal from three has to be accounted for at all times, even when he doesn’t have the ball. Gravity is the degree to which he pulls defenders into his sphere.

We tend to understand that simplistically, as in just what a player does with his shooting. But, as Zach Lowe explains for Grantland, while writing of Kyle Korver’s impact, it’s much more than that:

Great shooters have a gravitational pull, and they can shift the range of that force around the floor as they move. A defense can go haywire if that force collides with another object — a teammate screening for Korver, or a defensive player suddenly realizing that Korver has drilled him in the back with a nasty pick.

Dunleavy isn’t Korver, but if we were to liken Korver’s gravitational pull to that of the sun, we could say that Dunleavy’s is the moon.

And yes, the Bulls use Dunleavy’s spacing to open up three-point shooting for other players. That’s what gets Rose this wide-open three:

But the Bulls also use his gravitational pull off his screens. Here is why teams have to respect him when he rolls out after the pick:

The Bulls use that threat and his screens to create opportunities in the paint. If his defenders don’t stay with him, he scores. But if they do, he creates opportunities for his teammates to get to the rim.

Notice here how he sets a pick then rolls out to the baseline, taking his defender with him, creating an easy post-up situation for Butler in the process:

Here he sets the screen, and Travis Wear and Cole Aldrich are worried enough about him not getting between them that it sets up Gasol to get the dunk:

The purpose of spacing is that it opens up the court and provides inside scoring. The Bulls shoot 59.4 percent within the restricted area with Dunleavy and only 53.0 percent without him. They are 42.6 percent in the rest of the paint with him and only 39.0 percent without.

Dunleavy’s spacing makes the Bulls more efficient inside. Strategically, they are an inside-out team. Without him, teams have packed the paint, daring the shooters to beat them, and Chicago has typically been unable to meet that challenge.

No one has felt this more keenly than Butler, whose effective field-goal percentage with Dunleavy is 53.6 percent compared to just 46.7 percent without him. That’s because Dunleavy’s spacing opens up the court for Butler’s drives. Butler is 75-of-119 within five feet when Dunleavy is there and 68-of-121 when he’s not.

Dunleavy’s occasional three at a 41.7 percent clip is missed, but what’s missed more is how it opens up the paint for the Bulls. His absence is why they’ve been so much less efficient there.

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There will be those who misunderstand this article as trying to construe Dunleavy as the most important player on the Bulls. Rather, it’s just demonstrating that his role is critical because he helps the most important players to be their best. And that importance is magnified by his being the only true veteran small forward on the roster.

Can they get back to winning when he returns? They were doing fine until he got hurt. It’s an odd thing to say about a team that has made the playoffs the last two years without Rose, but the Bulls’ success this postseason will depend on Dunleavy being back and healthy.

Proprietary stats used courtesy of Vantage Sports. Other stats obtained from Basketball-Reference.com and NBA.com/Stats.