Thursday, April 26, 2018

2017 Yards Per Play: Pac-12

We'll stay out west this week as we review the Pac-12. Here are the 2017 Pac-12 standings.
So we know what each team achieved, but how did they perform? To answer that, here are the Yards Per Play (YPP), Yards Per Play Allowed (YPA) and Net Yards Per Play (Net) numbers for each Pac-12 team. This includes conference play only, championship game excluded. The teams are sorted by division by Net YPP with conference rank in parentheses.
College football teams play either eight or nine conference games. Consequently, their record in such a small sample may not be indicative of their quality of play. A few fortuitous bounces here or there can be the difference between another ho-hum campaign or a special season. Randomness and other factors outside of our perception play a role in determining the standings. It would be fantastic if college football teams played 100 or even 1000 games. Then we could have a better idea about which teams were really the best. Alas, players would miss too much class time, their bodies would be battered beyond recognition, and I would never leave the couch. As it is, we have to make do with the handful of games teams do play. In those games, we can learn a lot from a team’s YPP. Since 2005, I have collected YPP data for every conference. I use conference games only because teams play such divergent non-conference schedules and the teams within a conference tend to be of similar quality. By running a regression analysis between a team’s Net YPP (the difference between their Yards Per Play and Yards Per Play Allowed) and their conference winning percentage, we can see if Net YPP is a decent predictor of a team’s record. Spoiler alert. It is. For the statistically inclined, the correlation coefficient between a team’s Net YPP in conference play and their conference record is around .66. Since Net YPP is a solid predictor of a team’s conference record, we can use it to identify which teams had a significant disparity between their conference record as predicted by Net YPP and their actual conference record. I used a difference of .200 between predicted and actual winning percentage as the threshold for ‘significant’. Why .200? It is a little arbitrary, but .200 corresponds to a difference of 1.6 games over an eight game conference schedule and 1.8 games over a nine game one. Over or under-performing by more than a game and a half in a small sample seems significant to me. In the 2017 season, which teams in the Pac-12 met this threshold? Here are Pac-12 teams sorted by performance over what would be expected from their Net YPP numbers. Arizona State and Stanford significantly exceeded their expected record based on YPP and no Pac-12 team significantly under-performed relative to their expected record.
Arizona State finished with a decent record in close conference games, winning two of their three contests and the Sun Devils also had a decent in-conference turnover margin of +4. But we’ll have to dig a little deeper to uncover why their expected winning percentage is so low. The Sun Devils played poorly in just two conference games. In losses to the eventual Pac-12 Championship Game participants, Southern Cal, and Stanford, Arizona State was outgained on a per play basis by over two yards per snap (5.80 to 8.05). In their other seven games, the Sun Devils were much more competitive. In those seven contests, they were slightly outgained per play (5.59 to 5.63), yet they managed to win six of them. Credit Todd Graham’s voodoo and the vagaries of an even smaller sample size. Meanwhile, it’s much easier to see why Stanford exceeded their expected record. The Cardinal had the best in-conference turnover margin of any Pac-12 team (+12) and won all four of their one-score conference games. Those close games, especially the Friday night tilt with Washington, decided the Pac-12 North. That close game good fortune continued a trend under David Shaw. Since Shaw’s arrival on The Farm prior to the 2011 season, Stanford is 16-8 in one-score conference games.

The 2017 Pac-12 Championship Game was a rematch (or is it re-imagining?) of the 2015 Pac-12 Championship Game. Southern Cal was able to exact a modicum of revenge and claim their first ever Pac-12 title and first conference title since 2008! But, let’s go back to the 2015 game. Southern Cal won their first Pac-12 South title that season. It also marked the fourth consecutive year a different team won the division (with no repeats). Allow me to explain. UCLA won the South in 2012, Arizona State won it in 2013, Arizona won in 2014, and Southern Cal won in 2015. Colorado would extend the streak to five in 2016 before Southern Cal ended it in 2017.
How rare is a run of five unique champions in five seasons? Pretty darn unique. The only other Power Five conference that can boast a similar run is the ACC, with the Coastal division producing a unique champ in the past five seasons.
Outside of the Power Five, one conference can claim a longer streak, but it required some division shuffling which was a direct result of conference expansion.
By the time Rice won the West division of Conference USA, SMU, Houston, and Tulsa were members of the AAC. Louisiana Tech won the division in 2014; their second season in the conference after the WAC’s dissolution. Southern Miss was a charter member of the East division of the conference, but came over to the West following the league’s shifting in 2013.

If Utah can come away with the crown in 2018, every member of the Pac-12 South will have won the division. This would be a remarkable achievement considering the conference did not begin divisional play until 2011. The league would still not be able to match Conference USA in terms of egalitarian streaks, but it would be a distinctive accomplishment in its own right. And if either Virginia or Pitt claim the ACC Coastal in 2018, Conference USA will have company in terms of rotating division winners.

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