“Sink and Fill”
Term: Sink and Fill
Definition: A weak-side defensive rotation after dribble penetration in which one defender “sinks” into the legs of an offensive big around the basket and another “fills” into the lane to handle cutters or shooters.
Synonyms: Help the helper
Explanation: Offensive dribble penetration sets off a chain reaction of defensive rotations. The first is the two-nine man shifting from a centralized defensive position to trapping the box on the strong side. But this on-ball help throws two defenders at the ball — meaning three are left to guard the four remaining offensive players.
NBA defenses respond to this imbalance by prioritizing the most immediate threats relative to the driver. Assuming the first help defender prevents a direct scoring opportunity, the driver looks to pass with an inside-out progression: He checks for dump off passes for dunks before eyeing the weak-side for open, kick-out threes.
Sinking and filling as a whole eliminates these easiest options and encourages what’s left: the longest possible pass to the weak side. This is because the defense can theoretically scramble out of the sink-and-fill rotation during the flight time of the ball. And given the increased distance of the pass, anything thrown off-target gives the defense an additional tick to regroup.
This principle of forcing long, cross-court passes is a fundamental component of NBA defense. Remember that one-on-one dribble penetration is an assumption built into defensive concepts — no defender can stay in front of the ball at all times. That’s why the best defenses do not cut off every option; they guide the ball toward spots favorable for recovery. Sinking and filling accomplishes exactly that: It anticipates the obvious and narrows drive-and-kick options.
How To Sink
In non-ball screen situations, most NBA offenses maximize spacing with four players dotting the three-point line and one big lurking in one of the dunker spots. When an offensive player drives, the defender guarding this big is the natural trap-the-box man. This is where the sink-and-fill reverberation starts, because there is now an offensive player sitting unguarded next to the rim.
But who rotates to guard this open player? The “sink” man. While the four-on-three situation might suggest a weak-size zone to compensate, the close quarters of the potential dump-off pass makes it less feasible. That’s why NBA defenses use a man-to-man concept on this secondary layer of help. You double the ball, I got yours.
The “sink” man is the nearest perimeter player — typically on or around the weak-side elbow — to the open man in the dunker spot. Once his teammate leaves to trap the box, he:
- Immediately “sinks” down into the paint toward the open big.
- Gets ball-side — between ball and man.
- Hits the legs of the big.
Regarding the first point, trapping the box and sinking must be nearly simultaneous. All the driver needs is a tiny window to sneak a pass through to his teammate for a dunk. Every milisecond that big is left open is time for that pass to be completed. It is also why weak-side players creep into the middle when the ball is on the other side of the floor. They are prepping for this potential help-the-helper situation.
Because the sink man is dropping down from the perimeter, he is typically a wing player. And because that wing usually finds himself at a significant size disadvantage, this third point — hitting the big’s legs — is crucial.
Although getting ball-side is ideal, it isn’t always possible. The instantaneous nature of the sink rotation gives the defender little time to react. The offensive player also has natural inside position and does not give it up willingly. Dropping down low into a big’s legs, however, can accomplish the same goals by jamming him into the baseline. Not only does this throw him off balance and interrput the ease of a pass-catch, it also takes out his base of support. Should the driver shoot and miss, he is no longer an unencumbered offensive rebounder waiting for a put-back. Should the driver throw a lob over the trap-the-box defender, the receiving big is less likely to elevate. And if the driver tries to wrap a pass around the trap-the-box defender on the baseline side, the receiving big is wedged behind the backboard.
Take a look at how Tyler Ulis of the Phoenix Suns — giving up 15 inches in height to Myles Turner of the Indiana Pacers — successfully sinks in this defensive help rotation. As Paul George drives left against Devin Booker, Tyson Chandler steps up from two-nining to trap the box. Turner, meanwhile, tries to ancitipate the potential passing lane by stepping up into the gap vacated by Chandler.
A lot is on Ulis — he’s in the weak-side corner — to prevent an easy basket. If he allows Turner to seal him off to the outside, George has an easy pass for a dunk. Even if Ulis gets inside (ball-side), a short step forward by Turner creates room for a pass overtop. In short, he must physically greet the much stronger Turner early without giving up an inch of ground.
He doesn’t have to hold him off forever, as that would be impossible. He only has to do it long enough for George to see bodies and move off Turner as a dump-off option. Ulis ends up doing this by getting even lower than his 5'9 frame and hitting Turner first. And in that moment of contact with each player fighting for position, this is what George sees:
Who would you pass to? Remember that George is driving at speed with two defenders in his face and only a milisecond to evaluate his options. He sees Chandler’s hands in his vision; Ulis driving Turner under the rim; Marquese Chiss stunting and recovering back to Thad Young in the strong-side corner. Monta Ellis on the weak-side wing is at too difficult an angle for a pass. That leaves only one option: Fire a pass to Jeff Teague in the opposite corner. Ulis, having sunk effecively, sprints back to Teague and contests the shot.
How To Fill
“Sinking and filling” are woven together in one post here because they operate in tandem. Although “sinking” covers the most obvious passing threat after a drive, “filling” covers everything else: The “fill” man, who is on or around the strong-side elbow, literally fills up the paint alert for cutters.
What’s the first reaction of most off-ball defenders to a driving player? Look at the ball. What does every coach teach players to do when their man turns his head? Cut. This is why filling is so important.
Unlike the sink concept, filling has a zone component. While the fill man must be ready to return to his man on the kick-out pass, he is also potentially responsible for other weak-side perimeter players. In essence he is the defensive garbage man during dribble penetration — if anyone springs loose, he is there to pick them up. Sometimes, given the spacing of the offensive players, the two remaining defenders must both fill.
In order to properly fill, a defender must:
- Open his stance toward half-court.
- Fill to an appropriate depth.
It’s hard to guard multiple off-ball offensive players if you can’t see them. If the defender opens up his stance, he can track the ball and off-ball players peripherally. While this might not directly line himself up with anyone in particular, it optimizes his chances of recovery regardless of where the driver passes the ball.
There isn’t a single depth to which the fill man drops, because filling is situational. The deeper the drop, the larger the share of the floor a defender can see. But if the offense has four players standing still on the three-point line, filling too deep into the paint compromises a potential closeout on the kick-out. So the defender must read and react, dropping to an apporpriate depth that covers his bases.
That’s what Richard Jefferson of the Cleveland Cavaliers does on the play below as he defends Giannis Antetokounmpo of the Milwaukee Bucks from the nail. First, take note of the pre-fill defensive components at play here. Jabari Parker, prepping to drive, is shaded baseline by Tristan Thompson of the Cleveland Cavaliers; teammate LeBron James gets ready to trap the box; teammate Kyrie Irving gets ready to sink.
Although Jefferson deters middle penetration by dropping to the nail, he must also be ready to jump back to Antetokounmpo on an early kickout. It’s only when Parker gets deep that he can fill into the paint even more — he will have more time on the pass to recover.
If Jefferson stays tight to Antetokounmpo, he not only shirks his middle help responsibilities, but he leaves himself more vulnerable to a backdoor cut. (The tighter you are to an offensive player, the less room for error you have to react to their movements.) Also note how open Jefferson’s body is — he’s eyeing both ball and man without actually staring at either. A tiny change of footwork opens up the width of his vision, so much so that he could even contest a Matthew Dellavedova shot should he follow behind the ball.
As the play unfolds, Jefferson doesn’t react perfectly to Antetokounmpo’s cut. But it doesn’t matter because he has positioned himself appropriately so that Antetokoumpo has no choice but to cut through him. On contact, Jefferson feels the cut and takes it away.
Above is a more textbook trap the box, sink and fill scenario. Basketball, however, is typically messier. Take, for example, the play below as the Dallas Mavericks defend a drive by Dion Waiters of the Miami Heat. As Dwight Powell of Dallas traps the box, his man, Luke Babbitt of Miami, actually spaces out to the three-point line on the right wing.
Although Deron Williams’ fill here is not picture perfect, he drops enough to create defensive options. Teammate Seth Curry cannot leave the corner as that’s Waiters’ easiest pass. That leaves Williams to cover two players, James Johnson and Babbit. If he sticks to Johnson (his original man), Babbitt gets a wide open look. By filling, he gives himself a chance at a contest.
Film Study: “Sink and fill”
Below is a video compilation of various examples of defenders sinking and filling. Remember to keep your eyes peeled on the weak side. Most of the situations here aren’t clean, and it might not be easy to immediately identify the fill man. Sometimes the sink man is actually rotating out to the weak-side corner. Regardless of the situation, focus on how the defense rotates behind the initial trap-the-box help and see if you can spot the general sink-and-fill concept.
