Defensive Charting: Wake Forest

Here is an explanation of defensive charting and a look at how NC State's players fared against Wake Forest on the defensive end of the floor.

Defensive Charting Explained

First off, I'd be remiss if I didn't give full credit to the guys over at Duke Hoop Blog and Davis Hess at for inspiring this project and giving me some pointers before I started.

That said, the goal of defensive charting is simple – to assess what is actually happening on each defensive possession and give players appropriate credit (or blame) for the plays they make on defense.

Statistically, there is very little out there to show a player's value on defense – blocks and steals are such a small portion of defensive contribution but they are the only defensive statistics that are tracked.

By charting every play, we can get a much better idea of a player's true defensive value to his team. This is all done by hand with someone (in this case me) going through a game and charting each play.

Here's a look at the columns, both tracked and calculated, that are contained within each chart (definitions are taken directly from Duke Hoop Blog).

NOTE: For a full-sized view, click on the images themselves. The column sizes on the site make it impossible to fit an image large enough to read.

Taken from the traditional box score:
• Min – Minutes played

• DREB – Defensive Rebounds

Tracked directly by the charter:
• FM – Forced field goal Miss – when a defender forces an offensive player to miss a shot from the field. This includes blocked shots.

• FTO – Forced TurnOver – when a defender forces an offensive player to turn the ball over. This includes steals. One thing to note here is that a player who draws an offensive foul is always credited with a FTO, even if it's just a moving screen.

• FFTA – Forced missed Free Throw Attempt – missed foul shots resulting from a defender's foul

• DFGM – allowed Defensive Field Goal Made – when a defender's error or poor play leads to an offensive player scoring a field goal (intentional fouls at end of game excluded)

• DFTM – allowed Free Throw Made – made free throws resulting from a defender's foul (intentional fouls at end of game excluded)

Calculated Tallies:
• Stops – the credit a defensive player gets for actions that contributed to ending an opponent possession. This isn't as simple as adding FM + FTO + 0.4*FFTA, because the credit for a missed shot has to be shared with the defensive player who rebounds it. The formula is more complex than you might think, and includes a sliding weight for FM vs. DREB, based on how difficult those actions seem to be in each particular game.

• ScPos – Scoring Possessions allowed by a player. This is essentially just DFGM plus a FT-related factor.

• DPoss – [Stops + ScPos] – Total Defensive Possessions that were credited to (or blamed on) a player.

Calculated Metrics:
• Stop% – Stop Percentage — [Stops/DPoss] – The fraction of an individual player's credited defensive possessions that ended with zero points. Essentially the inverse of offensive Floor%.

• %DPoss – Defensive Possession Percentage — the percentage of team defensive possessions faced by an individual defender. Analogous to %Poss on offense.

• DRtg — Defensive Rating – Individual Defensive Rating gives a player credit for stops and scoring possessions he was directly involved in, then assumes a nebulous team-average performance in the other possessions. This is the analog of offensive rating. The lower a player's DRtg, the better he played defensively.


So what does this tell us?

Well we can immediately see that the two best defensive games came from Painter and Leslie – which should come as no surprise since they were guarding Le Forward Nikita and Ty Walker most of the game. Leslie's size was clearly a problem for Mescheriakov, who didn't try to do much other than take it directly at Leslie all night. Howell had a rougher time, as he was caught out of position or beaten off the dribble on several plays but his overall rating benefits from his team-high seven defensive rebounds.

The perimeter guys had a rougher time of it – C.J. Williams as usual had the toughest assignment of the night switching off between C.J. Harris and Travis McKie. While Williams still gets caught behind screens occasionally, he challenged a lot of shots, forced a lot of misses and caused a few turnovers as well.

Wood rates out as the worst defender of the day, a number that has more to do with his lack of rebounding than with his on the ball defense. Wood struggled fighting through screens and got lost in transition on one play that led to a McKie 3-pointer, but he rarely got beat off the dribble.

It's also interesting to note that while Alex Johnson was in the game, Wake targeted him on more than one out of every four possessions and had success. Johnson did force two turnovers, but neither Harris or Tony Chennault had much trouble scoring on the senior point guard.

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