FILM SESSION: Duke’s defensive tweak and what it means as they take on North Carolina

(AP Photo/Gretchen Ertl)
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The outlook of Duke’s season is significantly different today than it was three weeks ago.

That’s when the Blue Devils went down to Coral Gables and got dissected by Miami, losing 80-69 in a game where they gave up 1.27 points-per-possession (PPP) to a good, not great, offensive team. The Blue Devils had lost four of their last five games at that point, and they were a mess defensively. Amile Jefferson’s injury had sapped them of any interior depth they had, which forced them into playing Brandon Ingram exclusively at the four, and the coaching staff was still trying to figure out how to deal with that.

Playing their trademark, half court man-to-man defense created too many mismatches and resulted in too much foul trouble for a team that couldn’t afford to have any of their key players — they essentially use a six-man rotation with freshman Chase Jeter spelling Marshall Plumlee at times — sitting on the bench. The Blue Devils tried different variations of zone, but that has been an outright disaster; according to Synergy, Duke’s giving up 0.972 PPP when they play zone, which is in the 25th percentile nationally.

Over the course of the last two weeks, however, Duke has started to make some strides on that end of the floor, and it stems from a subtle tweak that they’ve made in their defensive philosophy: They’re not switching anymore.

Typically, in head coach Mike Krzyzewski’s half court man-to-man defense, the Blue Devils switch whenever possible. Sometimes it’s just like-to-like screens — when a guard screens a guard or a big screens a big — but generally speaking, they’ve switched all exchanges 1-through-4; from the point guard to the power forward, if two players screen for each other, run by each other or even just switch sides of the floor, Duke will switch. The theory behind this is that, while it creates mismatches at different spots on the floor, it also makes it a nightmare for the offense to run their sets and initiate actions where they want to on the floor.

This was quite prevalent the last two games, and it worked. Last Monday, Louisville scored just 24 points in the first half and Duke, in total, gave up less than 1.000 PPP, the first time they’ve done that against tournament-caliber opponent since they lost to Utah on Dec. 19th. They followed that up by holding Virginia — who, believe it or not, is the nation’s 12th best offensive team, according to KenPom’s adjusted offensive efficiency metric — to 1.052 PPP, which is nearly a 0.1 PPP off their season average.

That doesn’t sound like much, but in a 65 possession game, that’s a 6.5 point difference. It’s probably worth noting here that Duke is a 6.5-point underdog tonight against North Carolina.

Here’s what I’m talking about.

In this first example, Duke is trying to switch on a double ball-screen set by Indiana’s three and four, but for some reason three Blue Devils end up chasing the ball. The resulting confusion results in Marshall Plumlee trying to guard Troy Williams one-on-one.

Layup:

Here, you’ll see Ingram switch onto Notre Dame point guard Demetrius Jackson when Jackson, after making the pass to initiate offense, runs off of a flare screen. After Jackson receives the ball on the opposite side of the court, Ingram is too slow in trying to ice a side ball-screen — “icing” a screen means the defender guarding the ball doesn’t allow the ball-handler to go over the screen, keeping the ball pinned on the sideline — which allows Jackson to get into the teeth of the defense.

After some horrid help defense … layup:

Now watch this possession from the win over Virginia. Not only does Duke not switch a single screen or exchange, but Plumlee camps out in the lane much the way that he would if he was the middle of a 2-3 zone:

The other major difference during this four-game winning streak is that the Blue Devils are actually starting to get on the glass a little bit.

On the season, Duke is 279th in defensive rebounding percentage, allowing opponents to grab 32.3 percent of their available offensive rebounds. In ACC play, that number is 33.6 percent, with the problem coming to a head against Syracuse, when the Orange grabbed an insane 26 offensive rebounds. But again, the last four games — and particularly the last two — have been a different story. Duke is getting more than 70 percent of the available defensive rebounds — which would be fourth in the ACC at this moment — despite three of the four opponent during that streak sitting in the top six in offensive rebounding in the league.

Against Louisville and Virginia last week?

Duke allowed a total of just 15 offensive boards.

Now, part of this is due to their scheme. When you’re playing a straight man-to-man, it’s a lot easier to protect the defensive glass. In zone, it’s difficult to find someone to box out. In a switching man-to-man, mismatches abound; bigs have to try and box out quicker guards on the perimeter while Duke’s little guys are forced to try and keep some of the ACC’s best big men from getting to the glass.

In a straight man-to-man? It’s all about effort, pride and understanding the angles. Can I keep my man from beating me one-on-one to the loose ball? Do I know where the ball is going to bounce off the rim? There’s a reason, when you talk to scouts at any level, you’ll hear them say, “rebounding translates.”

It’s a skill, one that North Carolina has in abundance.

This is where Wednesday night’s game will be won: on the glass.

More specifically: Will Brandon Ingram be able to hold his own on the glass against North Carolina’s NBA-caliber front line?

Ingram is the ultimate matchup problem. At 6-foot-9, Ingram is a natural small forward, with a sweet shooting stroke, a smooth mid-range game and enough handle to both initiate offense and beat a slower defender off the dribble. He gets the opportunity to do the latter quite often for Duke, as he spends all of his time playing the power forward spot in the same way that Justise Winslow did last season and Jabari Parker did before him.

The problem is that where Winslow was an elite defender, Ingram is more like Parker when it comes to being a defensive stopper, particularly in the post. He’s thinner than Taylor Swift and, for much of the season, was probably just as physical as her in the paint. Can he keep Brice Johnson and Isaiah Hicks off the offensive glass? Can he handle Kennedy Meeks or Joel James in the post?

And in the end, I think that’s what this game is going to come down to.

Who forces whom to make a change?

Against Virginia, after digging themselves an 11 point first half hole, Duke for Virginia to go small when Ingram made seven straight shots and scored 18 consecutive Duke points while Virginia’s bigs were trying to guard him. Tony Bennett was forced to put Malcolm Brogdon on Ingram and play a four-guard lineup, which took away from what UVA likes to do offensively.

Can Ingram do the same against North Carolina?

Or will the Tar Heels simply be able to overpower him inside?