Defense and the “Fifth Factor”

Title: Defense and the “Fifth Factor”
Date: November 25, 2012
Original Source: Hoopdata
Synopsis: This article looked at what impact a team’s pace of play has on their defensive efficiency, asking if pace should be considered the Fifth Factor in determining defensive success.

On a recent Raptors Republic podcast, a show I host each week, one of the panellists suggested that he thought the Raptors’ decline in defense may have been due to them playing at a faster pace this season.

No, the analysis wasn’t based on a faulty mathematical basis – he was not mistaking, as many did during the D’Antoni-era in Phoenix, that a faster pace led to more points and more points were indicative of a bad defensive unit. Instead, he was suggesting that, even for an efficiency stat like defensive rating, pace could still have an impact.

It’s a fair point. Basically, if a team was successful slowing the game down and forcing teams to operate in the half court more, speeding up the game could expose things like poor transition defense, less capable individual defenders, and more.

So, taking his comment and running with it, I pulled some defensive data from Basketball Reference for the past few seasons, dating back to 2007-08. I was first interested to see if teams who played at a faster pace tended to have a worse Defensive Rating. The relationship between pace and defensive rating is shown in the graph below – the relationship had a correlation of 0.29 and an R2 of 9%. The p-value was insignificant, meaning that, even though the relationship isn’t strong, it still exists, and faster-paced teams do tend to be of poorer quality on defense.

I found this to be a bit interesting, as my initial assumption was that, while my panelist’s argument made sense intuitively, pace is normally not discussed as a factor in defensive rating. In fact, the “four factors” that are most commonly discussed are Opponent’s Effective FG% (eFG%), Turnover Percentage (TOV%), Defensive Rebound Rate (DRB%) and Free Throws per Field Goal Attempts (FT/FGA). The “Four Factors” of defense had individual correlations with Defensive Rating as follows.

You can see from the table that an opponent’s eFG% has by far the strongest correlation with Defensive Rating, which makes obvious sense. Adding pace to our “Four Factors” to give us a “Five Factors” model adds very little to our understanding of what makes a good defense, so it seems a waste.

However, is it possible that pace has an impact on eFG%? This would be helpful, since a team looking to improve its Defensive Rating can’t really just say “get more stops” to improve defense. Instead, if pace has an obvious impact on eFG%, teams can then look to slow things down to improve their defense, along with forcing more turnovers, fouling less, and doing a better job on the boards (essentially, I wanted to know if we can replace “get more stops” with a more practical suggestion for teams).

Like with pace and Defensive Rating, we see a somewhat weak but statistically significant relationship. Thus, we can safely suggest to coaches that slowing down the pace should have a small positive impact on defensive rating.

Thus, our “Four Factors” should now be: *Defensive Rebound Rate – crash your own boards harder, box out more, leak out less *Turnover Rate – force more turnovers *Free Throw Rate – send teams to the line less *eFG% – get more stops, which can be aided by slowing down the pace

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