Saturday night, somebody noticed that Saint Louis had a horrible defensive 3P%. The first effects of the post-Rick Majerus era, right? Not really. It\u2019s because the defense has little control over its opponents\u2019 3P%. As an illustration, let\u2019s look at the best and worst \u201cthree-point defenses\u201d in previous seasons on December 4th, and examine how they fared the rest of the season.<\/p>\n
What I\u2019ve done is taken both the top 20 and bottom 20 teams in opponents\u2019 3P% as of 12\/4 each of the last four seasons, and recorded their three-point defense from December 5th onward. All figures are averages for the 20 teams in each group.<\/p>\n
Thru 12\/4 After 12\/4\n Top 20 Bottom 20 Top 20 Bottom 20<\/u> \n2012 45.2 23.8 34.8 32.9 \n2011 44.6 24.7 34.6 33.3\n2010 45.1 24.6 35.4 34.0\n2009 44.5 23.9 34.3 34.2\n Avg 44.9 24.3 34.8 33.6\n\n<\/pre>\nSo on average over the rest of the season, there will be a roughly a 1-2 percent difference between the teams currently in the top and bottom 20 of opponents\u2019 3-point percentage. We\u2019re talking about a difference of one make every two or three games between the best and worst groups. Without more analysis, one can\u2019t say precisely how much skill a team has at influencing its opponents\u2019 three-point percentage, but there\u2019s a fair amount of evidence it\u2019s not much, and even end-of-season figures are the result of significantly more noise than skill. <\/p>\n
With few exceptions, the best measure of three-point defense is a team\u2019s ability to keep the opponents from taking 3\u2019s. This is what the Majerus defense did, and fortunately for Billiken fans, Jim Crews is carrying on that tradition as SLU is currently allowing the nation\u2019s second-fewest 3PA%.<\/p>\n
When people say that advanced-stats users are a bunch of nerds, I can only think the people that don\u2019t use them are the real dorks. Nobody with any knowledge of the game would talk about free throw defense using opponents\u2019 FT% as if it was a real thing, yet we\u2019ll hear plenty of references to three-point defense in that way from famous and respected people. Of course, both free-throw defense and three-point defense exist, but it\u2019s much better measured in the amount of shots taken and not in the noisy world of the percentage of shots an opponent makes.<\/p>\n
For reference, here\u2019s a rough analysis of how well various team shooting stats currently identify greatness (or awfulness). The left column is the 12\/4 difference between the average of the top 20 and bottom 20 in each category, and the right column is the difference between the same groups of teams ove the rest of the season. Essentially, the larger the difference going forward, the less noise the stat contains. Only data from last season is used in this comparison. <\/p>\n
Pre 12\/4 Post 12\/4\n Diff Diff <\/u>\nOpp FT% 19.7 1.7\nOpp 3P% 21.4 1.9\nOwn 3P% 21.7 3.6\nOpp 2P% 20.9 4.8\nOwn 2P% 19.6 5.5\nOwn FT% 22.1 8.5\nOpp 3PA% 20.7 9.7\nOwn 3PA% 24.1 14.5 \n\n<\/pre>\nWhen someone discusses three-point defense in terms of three-point percentage, they might as well make the leap to discuss free-throw defense in similar terms. Teams have much more control over how many three’s their opponents shoot than how many they make.<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
Saturday night, somebody noticed that Saint Louis had a horrible defensive 3P%. The first effects of the post-Rick Majerus era, right? Not really. It\u2019s because the defense has little control over its opponents\u2019 3P%. As an illustration, let\u2019s look at the best and worst \u201cthree-point defenses\u201d in previous seasons on December 4th, and examine how […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/posts\/364"}],"collection":[{"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/comments?post=364"}],"version-history":[{"count":1,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/posts\/364\/revisions"}],"predecessor-version":[{"id":2397,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/posts\/364\/revisions\/2397"}],"wp:attachment":[{"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/media?parent=364"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/categories?post=364"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kenpom.com\/blog\/wp-json\/wp\/v2\/tags?post=364"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}