February 3, 2012
Defending the Three
Meaningful Stat?

by Dan Feldman

Phoenix Suns coach Alvin Gentry doesn't believe in judging a team's three-point defense by the most common metric used to do so: three-point percentage.

"I don't buy into that," Gentry said of a given team's supposedly strong defensive numbers against the three-point shot. "I think that's the worst stat in the NBA, defending the three. I think teams either shoot it well against you or they don't. You know, most of the three-point shots that are taken are open shots; people are usually not forcing three-point shots."

"Maybe they close out better or they do a good job of running you off, I don't know," Gentry said. "It's just not a stat I think is relevant at all, I really don't."

Even if Gentry's assertion--that teams have little control whether an opponent makes a three-point attempt--is correct, it stands to reason teams could at least limit three-point attempts.

In the previous five years, 11 teams ranked either in the bottom 10 or top 10 of three-point-percentage defense for three straight seasons:

• 2009-11 Lakers (3, 1, 3)
• 2009-11 Hawks (4,9,7)
• 2009-11 Celtics (5, 4, 5)
• 2009-11 Timberwolves (27, 25, 22)
• 2008-10 Celtics (4, 5, 1)
• 2008-10 Nets (27, 29, 24)
• 2007-09 Cavaliers (1, 10, 11)
• 2007-09 Pistons (9, 2, 4)
• 2007-09 Bucks (23, 27, 25)
• 2007-09 Wizards (27, 30, 29)
• 2007-09 Kings (30, 25, 23)

In the same span, 18 teams ranked either in the bottom 10 or top 10 of fewest three-point attempts allowed per possession for three straight seasons:

• 2009-11 Rockets (1, 4, 4)
• 2009-11 Spurs (2, 1, 1)
• 2009-11 Kings (3, 6, 8)
• 2009-11 Thunder (4, 8, 9)
• 2009-11 Bobcats (29, 30, 24)
• 2009-11 Lakers (30, 24, 27)
• 2008-10 Spurs (1, 1, 4)
• 2008-10 Rockets (4, 4, 2)
• 2008-10 76ers (22, 26, 26)
• 2008-10 Raptors (28, 29, 29)
• 2007-09 Spurs (1, 4, 2)
• 2007-09 Pistons (3, 5, 8)
• 2007-09 Mavericks (7, 1, 1)
• 2007-09 Knicks (21, 28, 27)
• 2007-09 Nuggets (25, 24, 21)
• 2007-09 Hornets (28, 27, 30)
• 2007-09 Raptors (29, 29, 23)
• 2007-09 Wizards (30, 30, 29)

That certainly indicates preventing three-point attempts is more manageable than stopping teams from making them.

If Gentry is correct, the Spurs play the model perimeter defense. After all, teams have the best effective field-goal percentage--aside from shots on the rim--on three-pointers. So, especially if teams can't really affect a three-point shooter's likelihood of making his shot, defenses should try to force two-point jumpers.

In the previous 10 years, the Spurs have finished anywhere between second and 24th in three-point-percentage defense. But they've always ranked in the top four of three-point attempts allowed per possession.

Three-point-percentage defense is orange, and three-point attempts allowed per possession is blue.

Gentry also compared defending three-pointers to defending free throws:

"I think teams shot worse against us from the foul line last year; I think we were in the top five," Gentry said. "I don't know that we did a whole lot to defend the free throw line."

Maybe he's onto something. In the previous five years, 14 teams ranked either in the bottom 10 or top 10 of free-throw-percentage defense for three straight seasons--more than the 11 teams who qualified with three-point-percentage defense.

• 2009-11 Magic (1, 10, 3)
• 2009-11 Nets (6, 6, 10)
• 2009-11 Bucks (21, 23, 28)
• 2009-11 76ers (24, 24, 25)
• 2009-11 Warriors (26, 25, 23)
• 2009-11 Timberwolves (28, 29, 22)
• 2008-10 Bobcats (1, 4, 6)
• 2008-10 Knicks (9, 6, 3)
• 2008-10 Bucks (23, 28, 22)
• 2008-10 76ers (24, 25, 28)
• 2008-10 Timberwolves (29, 22, 26)
• 2008-10 Raptors (30, 26, 30)
• 2007-09 Timberwolves (22, 26, 25)
• 2007-09 Trail Blazers (30, 24, 30)

Dan Feldman is an author of Basketball Prospectus. You can contact Dan by clicking here or click here to see Dan's other articles.