As we have discussed on CB ad nauseum, the number of wins in a season means nothing when taken out of context. So instead of counting wins, let's use RPI and Pomeroy ratings, which take into account W/L, SOS, and other metrics. I'll also list postseason performance.
BYU under Coach Rose
Year- RPI - Pomeroy - Postseason
2006 - 71 - 92 - NIT
2007 - 20 - 45 - NCAA Round of 64
2008 - 25 - 35 - NCAA Round of 64
2009 - 37 - 21 - NCAA Round of 64
2010 - 28 - 10 - NCAA Round of 32
2011 - 8 - 11 - NCAA Sweet 16
2012 - 47 - 50 - NCAA Round of 64
2013 - 58 - 57 - NIT
2014 - 38 - 48 - NCAA Round of 64
2015 - 43 - 28 - NCAA First Four
2016 - 67 - 53 - NIT
2017 - 97 - 82 - ? (almost certainly NIT)
First 6 seasons average RPI: 31.5
First 6 seasons average Pomeroy: 35.7
First 6 seasons NCAA Tournament appearances/wins: 5/3
Last 6 seasons average RPI: 58.3
Last 6 seasons average Pomeroy: 53.0
Last 6 seasons NCAA Tournament appearances/wins: 3/1
By any objective measure, Rose's last 6 seasons have been worse than his first 6.
"But wait!" you may say. "That's not a fair comparison. We got really lucky to have a once-in-a-lifetime player with Jimmer!"
Okay, then, let's discount the Jimmer effect by just taking Rose's first 3 Jimmerless seasons vs. his last 3 (technically Jimmer played in 2007-08, but he averaged only 7 ppg.)
First 3 seasons average RPI: 38.7
First 3 seasons average Pomeroy: 57.3
First 3 seasons NCAA Tournament appearances/wins: 2/0
Last 3 seasons average RPI: 69
Last 3 seasons average Pomeroy: 54.3
Last 3 seasons NCAA Tournament appearances/wins: 1/0
A closer call, but it's still pretty clear that Rose had more success overall in his first 3 seasons than his last 3. This current season is at least his worst since his first season, and arguably his worst season ever.
And keep in mind that these last 3 seasons have included: the senior season of BYU's all-time leading scorer (Haws), perhaps its best all-around performer (Collinsworth), and its highest-ever recruiting class. Yet results are worse now than when Rose started. Now you start to see why we say Rose is underperforming in a big way.