Just clicking around the college football internets. I was wondering about the average of great run defenses in this newish world of read-option football. Here's some stuff I found:
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I was just looking at the top few P5 rush defenses, so I set the cutoff at 90 ypg allowed.
At this cutoff, the per-year range varies from zero (2017) to ten (2006).
There are definitely fewer elite rush defense teams recently, as there are 0-2 teams below 90 ypg allowed in each of the past seven years (only 5 in the past 5 years).
The average earlier in the century are 5-6 per year, with individual seasons of 10, 7, and 6.
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Here's the best of the past 21 years:
ypg allowed: year team
43: 2006 Michigan
59: 2006 Texas
60: 2003 USC
62: 2003 Ohio St
63: 2016 Alabama
66: 2006 Miami
67: 2003 LSU
68: 2007 Boston College
69: 2004 Florida St
70: 2002 Kansas St, 2019 Utah
72: 2009 Texas, 2011 Alabama, 2020 Georgia, 2001 VA Tech
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I'll stop here and note that 2011 Alabama had the 12th-best rush D of the new century AND probably the best pass defense ever. That's nuts.
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Another note is TCU. They're among the leaders sprinkled through the years, but weren't P5 yet. However, in 2008, they allowed only 49 ypg rushing, which is special.