Duke was one of the worst defensive teams in the country. Then it started playing zone.
Duke has had one of the country’s best offenses all season. The Blue Devils rank second in offensive efficiency, sixth in scoring offense, and it is not outside the realm of possibilities that all five of their starters are selected in the 2018 NBA Draft this June. Duke gets buckets. Full stop.
The Blue Devils’ problem for much of the year came on the other side of the ball. For most of the season, Duke ranked outside the top-70 in defensive efficiency. Mike Krzyzewski’s team allowed an average of 72.3 points per game from the start of the season until February 8 – its first game against North Carolina – and 79.4 points per game against major conferences teams (not including Pitt, which doesn’t deserve to be considered a major program this year).
Throughout that part of the season, Krzyzewski held firm to his man-to-man defensive principles. Krzyzewski has famously employed a man-to-man defensive scheme his entire career, which makes sense considering he studied under Bob Knight, a strict adherent to that style.
Unfortunately, this Duke team couldn’t play a lick of man defense. Perimeter defenders were constantly beat off the dribble, interior defenders couldn’t protect the rim, nobody seemed capable of closing off shooters around the three-point line, and the Blue Devils were forced to score obscene amounts of points to win close games.
Eventually, the poor defense caught up with them. Duke dropped resounding duds against Boston College and N.C. State during which the Blue Devils allowed 185 points combined, then dropped three out of four a month later. That mini-skid included a loss to St. John’s which was, at that point, on an 11-game losing streak.
For this extremely talented Duke team to succeed in its national championship aspirations, it needed to make drastic changes.
It started to in mid-January. At around that time, Krzyzewski started to go to a 2-3 zone at different points throughout games to at least create a change in look for opposing offenses. As the season continued, the zone defense consistently frustrated opponents, and the man defense consistently was, for lack of a better word, very, very bad.
Then came the full commitment. Since their February 11 game against Georgia Tech, the Blue Devils have almost exclusively employed a 2-3 zone defensively, and it has worked phenomenally.
During its past six games, Duke is allowing just 57.0 points per game and has jumped up to 15th in defensive efficiency. That sort of midseason improvement is unheard of and is critical to the Blue Devils’ chances of cutting down the nets in April. As my colleague Joe Ilardi pointed out a couple weeks ago, since 2002, the overwhelming majority of teams that won the national title (12 out of 16) were top-15 in both offensive and defensive efficiency.
That cut off is arbitrary but the point is clear: it is extremely difficult to win a national championship if you are great at just offense or just defense. You need to be great at both and thanks to this shift to the zone, Duke is now great on both sides of the ball.
So why has this shift in scheme been so effective for the Blue Devils? Moving to the zone addresses the pitfalls of the enormous amount of youth up and down Duke’s lineup, and takes advantage of its enormous length.
Playing solid man-to-man defense requires an enormous amount of individual effort, excellent communication, and a complex understanding of assignments (e.g. when to switch on ball screens vs. when to fight over the screen and stay with your man).
No matter how historically great a coach is, it’s difficult to convince an 18-or-19-year-old freshman headed to the NBA in a few months to give full effort on every defensive possession. That’s problematic for running a truly effective man-to-man scheme.
For a team made up of almost all freshmen, it is even harder to develop the kind of vocal and intuitive communication necessary for successful man defense because these kids haven’t played together for a particularly long period of time. It is most difficult of all for these kids to truly understand what to do in every single situation that can arise throughout a basketball game. It is not yet instinctual when to follow an off-ball screen and when to let him release because the defender knows his teammate will be there to cover him.
By playing a zone, everything is simplified for the defender.
The 2-3 zone is called such because it puts a team’s two smallest players (read: guards) up top in two different zones along the perimeter, its biggest defender sits in the paint around the basket in his zone, and the two remaining defenders occupy zones down low near the corners.
The four defenders around the perimeter can pinch a bit toward the paint and rotate along the three-point arc if necessary (depending on the offense’s spacing), but no player has to worry about more than his own particular zone. There isn’t any excessive movement, there is no switching, and there is not much thinking involved. That makes defending a lot easier for a first-year player.
Using a zone defense also allows the Blue Devils to take advantage of their natural length.
Duke’s regular guards – Grayson Allen, Trevon Duval, and Gary Trent Jr. – are 6-foot-5, 6-foot-3, and 6-foot-6, respectively, giving Krzyzewski a very tall backcourt with which to work. Duke’s other regulars – Marvin Bagley III, Wendell Carter, Marques Bolden, and Javin DeLaurier – are all either 6-foot-10 or 6-foot-11, and occasional subs Alex O’Connell and Jack White are 6-foot-6 and 6-foot-7, respectively.
Everyone on the floor for Duke is tall for their position. They all have long wingspans that allow them to shift in the zone and cover so much space to deny the ball, make penetration extremely difficult, and help all spots on the floor. The zone naturally helps protect the paint, but Duke’s length makes it even more difficult to drive to the lane or post-up.
It also helps the Blue Devils account for one of the zone’s main weaknesses: rebounding. Because an offense can use its spacing to draw defenders away from the basket, it can make defensive rebounding difficult if multiple offensive players crash the boards against the lone center. Because Duke’s players are so long, that lonely center, whether it’s Bagley, Carter, Bolden, or DeLaurier, generally does not have an issue securing the rebound on his own. The Blue Devils rank fourth nationally in rebound margin.
The zone does have two natural holes: the elbow and the deep pocket below the basket. However, few college offenses have players with consistent midrange games to take advantage of the elbow or the patience to continually work the deep pocket with smart passing.
Moving to make the zone defense Duke’s primary look was a stroke of genius for Krzyzewski, and probably a semi-frustrating one for a person so committed to the man scheme. This isn’t the first time Krzyzewski has made a move to zone midseason, though.
Way back in 2014-15, Krzyzewski had an extremely talented, albeit young team that struggled defensively throughout the first half of the season. Then, around February, Krzyzewski started utilizing the 2-3 as the primary scheme. That team won a national title.
That doesn’t mean Duke is guaranteed to win anything, but it does show that this move has worked before. The Blue Devils offense has stumbled a bit the past two games, scoring just 60 and 63 points, respectively, but the offense will return. There are too many talented, multi-faceted scorers on this roster for it not to come back, and soon.
If Duke brings home its sixth national title, it will be because it successfully committed to drastically improving its defense.
Edited by Jeremy Losak.
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