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Statistically Speaking: Pac-10 Look-Ahead: SDPI

Sunday, February 24, 2008

Pac-10 Look-Ahead: SDPI


One of my favorite set of posts from last offseason was the conference recap using SDPI. SDPI is a statistic I borrowed from Eddie Epstein that he used in his book, Dominance, to rank pro football's all-time greatest teams. SDPI stands for Standard Deviation Power Index and looks at how teams performed relative to the league average (or conference average in this case) and standard deviation in terms of points scored and allowed. The more standard deviations a team is above the mean, the better they are, and vice-versa. Here is the link to last year's Pac-10 post. As you can see, SDPI was a useful tool in predicting some of the rise and fall among the Pac-10's teams. In the interest of providing an even better offseason analysis, I will now be conducting another SDPI, this time for yardage. It is calculated in the same manner as the SDPI for points, but will obviously be measured against the conference mean and standard deviation for yards. Think of it this way: Points are the end result and yards are the means to that end. Thus, looking at both sets of data, we can get an even better idea about which teams are likely to improve or regress in 2008.

If you want the meat of the article, skip this next paragraph as it just gives an example of how the SDPI is calculated. The mean points scored and allowed for all Pac-10 teams in conference play was 240.6 points. The standard deviation for points scored was 43.80. The standard deviation for points allowed was 51.13. Arizona scored 257 points in Pac-10 play and allowed 249. Their offensive SDPI was 0.37 = ([257-240.6]/43.80). Their defensive SDPI was -0.16 = ([240.6-249]/51.13). Their total SDPI for points (SDPIP) was 0.21 which ranked 6th in the conference. The mean yardage for and against for all Pac-10 teams in conference play was 3435.9 yards. The standard deviation for yardage for was 376.58. The standard deviation for yards allowed was 578.27. Arizona gained 3393 yards in conference play and allowed 3410. Their offensive SDPI was -0.11 = ([3393-3435.9]/376.58). Their defensive SDPI was 0.04 = ([3435.9-3410]/578.27). Their total SDPI for yards (SDPIY) was -0.07 which ranked 7th in the conference.

To refresh your memory, here are the 2007 Pac-10 Standings.

Now here are the 2007 SDPI standings.

Points wise, SDPI conforms pretty well with how things shook out. However, there certainly are some surprises when we look at yardage. For starters, Washington State and California, winners of only 1/3 of their Pac-10 games in 2007, rank ahead of Arizona State, the league's co-champ. How can this be? The Sun Devils began the season 7-0 and their only blemishes in conference play were to the league's top two teams; Southern Cal and Oregon (with Dennis Dixon). As is often the case, the simple answer is turnover margin. The Sun Devils led the Pac-10 with a +7 turnover margin in conference play. On the other hand, Washington State and California finished at the bottom of the league with a -4 and -6 margin respectively. The yardage differential also fleshes out just how bad Stanford was, relative to the rest of the league. Despite finishing a game ahead of Washington, tied with Washington State and California for 7th place, the Cardinal had both the worst offense and defense in the league.

Best Offense: Oregon 1.38 (SDPIP) and 1.46 (SDPIY)
The Ducks still ranked as the best offense in the Pac-10 despite the absence of Dennis Dixon for the last 2 and 3/4 games. In the 6 Pac-10 games Dixon started and finished, the Ducks averaged 506 yards per game. In the 3 he did not finish, they averaged 317 yards per game.

Worst Offense: Stanford -2.11 (SDPIP) and -2.03 (SDPIY)
Stanford gained the fewest yards and scored the fewest points. They averaged 146 fewer yards and 17 fewer points per game than the top-ranked offense in Eugene.

Best Defense: Southern Cal 1.77 (SDPIP) and 2.02 (SDPIY)
Only two Pac-10 teams gained over 300 yards against the Trojans--Oregon and California.

Worst Defense: Washington -1.57 (SDPIP), Stanford -1.42 (SDPIY)
At this point, it really is take your pick. They were both horrible.

Looking ahead to next season, the prohibitive favorite should be...

Southern Cal
If there is one thing this blog does, its go out on a limb. The underdog Trojans have a shot at the Pac-10 title if things break their way. Who are we kidding? The Trojans have 3 co-championships and 3 out-right titles the past 6 seasons. If you're bad at math, that means they have earned at least a share of the last 6 Pac-10 championships. All signs point to lucky number 7 in 2008.

The team(s) that will improve are...

California and Washington State
If you're curious, Jeff Tedford did not forget how to coach in 2007. The Bears suffered through easily the worst season of the Tedford era in 2007. However, if we look at their yardage differential (a pretty good indicator of down to down success), the Golden Bears were about the 4th best team in the conference. Their undoing in 2007 was their proclivity to turn the football over. Their turnover margin of -6 was the worst in Pac-10 play. In their first two conference games, they defeated Arizona and Oregon and had a turnover margin of +6. In their last 7 conference games, they won only once and, not surprisingly, lost the turnover battle in each game (-12 in that span). Expect the Bears to migrate toward the middle of the league in turnover margin and jump a few spots in the standings as well. Based on the yardage incarnation of SDPI, the Cougars were one of the better teams in the Pac-10. Behind the efficient passing of quarterback Alex Brink, the Cougars finished behind only Oregon in yards gained in Pac-10 play. Unfortunately, their defense betrayed them. Only Washington and Stanford allowed more yards in conference play. Despite losing Brink to graduation, the Cougars could make a push at a bowl bid in the uber-competitive Pac-10 thanks to a few factors.

1. Their turnover margin of -4 was second to last in the Pac-10. Turnovers and turnover margins are highly variable, so its highly likely the Cougars will be more fortuitous in this department next season.
2. The defense, by all rights pretty bad last season, does get 8 starters back including the two leading sackers, Andy Mattingly and Greg Trent (both linebackers).
3. Brink is gone as well as one starting receiver and tight end, but the leading receiver, Brandon Gibson, is back for his senior season. The two leading rushers, Dwight Tardy and Christopher Ivory, both return. Plus the starting quarterback (Gary Rogers), while he lacks experience, is a senior.
4. The new head coach, Paul Wulff has been reasonably successful at IAA Eastern Washington. Wulff's teams have posted winning records in 7 of his 8 seasons and made the playoffs 3 of the last 4 seasons.
5. The Cougars' luck just has to change.
The above table lists the yardage each Pac-10 has accumulated and allowed the past 3 seasons. The Cougars have basically played their opponents even over the past 3 seasons, as they have been outgained by 2 yards over 26 games. Unfortunately, that has not correlated to any success in the won/loss department as the Cougars have fared better than only Stanford over that span. If only they had the good fortune of the Bruins. UCLA has been outgained on the year each season, yet has finished no worse than 5-4 in Pac-10 play and actually boasts the second best conference record over that span.

Before we leave the Cougars, I feel the need to tout the accomplishments of departing signal caller Alex Brink. Brink will never be as revered as his predecessors in Pullman, Drew Bledsoe, Ryan Leaf, and Jason Gesser, because he never led the Cougars to a bowl game. However, Brink has been an outstanding quarterback and his accomplishments should not be forgotten because his teammates were not as good.

The team(s) that will decline are...

Arizona State and Oregon State
Dennis Erickson's first season in Tempe was a great success, resulting in a Pac-10 co-championship. Unfortunately, his encore performance will not be quite as good. For starters, the Sun Devils performance placed them around the middle of the pack in the Pac-10. They were 3-0 in one-score conference games, so instead of evaluating them as a 7-2 conference champ, it would probably be more prudent to consider them a 6-3 or 5-4 mid-level Pac-10 team heading into 2008. The Sun Devils should also see some regression in their turnover margin. The Sun Devils led the Pac-10 with a +7 margin in conference play. Should that number come down, which it likely will, the Sun Devils record will follow suit. Finally, thanks to the Pac-10's 9-game conference slate, the Sun Devils must play more than half of their conference games on the road. After beginning the season 2-4 (0-2 in Pac-10 play), the Beavers won 7 of their last 8 games, losing only to the Trojans. However, their margin of error was razor thin. They parlayed an excellent defense, second to the Trojans in yards allowed in conference play, a good turnover margin, tied for second at +5, and a little luck, 3-0 in one-score conference games, into a 6-3 conference record. With such great success on defense, why did the Beavers fail to win the conference crown? Because the offense was just plain bad. They finished 8th in the league in yards gained. Neither sophomore quarterback, Sean Canfield or Lyle Moevao, was able to throw more touchdowns than interceptions, compete 60% of their passes, or average over 6 yards per pass. In 2008, the Beavers can expect their turnover margin and general good fortune to regress. Thus, they need improved quarterback play, especially with the loss of senior running back Yvenson Bernard. However, even if they get that, the defense loses a ton of talent and will probably not be as strong next season. The Beavers main strength on defense in 2007 was tackling opposing ball carriers in the backfield (6th in the nation), and more specifically, generating sacks (10th in the nation). Of the 6 gentlemen with 10 or more tackles for loss, 4 are gone. Only defensive linemen Victor Butler and Slade Norris remain. The Beavers will have a tougher time getting into the backfield in 2008, and this will not be offset by enough improvement from the offense.

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