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Statistically Speaking: Big 10 2008 SDPI

Tuesday, February 17, 2009

Big 10 2008 SDPI

One of my favorite set of posts from the past two offseasons has been the SDPI recap/early preview. Don't know what SDPI is? It stands for Standard Deviation Power Index and is a tool Eddie Epstein used in his book Dominance to rate pro football's best teams. The basic idea is to look at how far above or below average (by standard deviations) a specific team is relative to their conference brethren. Since each team plays the same number of conference games, it can give us a good idea about who the best team was within the conference. However, it cannot tell us which conference is better. But the purpose of these posts is not to determine which conference is superior, but rather project ahead which teams in a conference will be contenders or also rans in the upcoming season. In the first post on SDPI two years ago, I calculated SDPI based on points scored and allowed within conference play. Last season I used points scored and allowed as well as yards gained and allowed. This season, I'm sticking with yards only. The yardage version of SDPI has a better correlation with future performance than points, and including both last season made the post seem (at least to me) quite muddled. Of course, this is by no means, the end all be all rating system, but it can give us an idea of which teams will improve and decline in 2009. We've already looked at the ACC and Big East, so now its time to turn our attention to the midwest and examine the Big 10.

If you want the meat of the article, skip this next paragraph as it just gives an example of how SDPI is calculated. The mean yardage for and against for all Big 10 teams in conference play was 2813.64 yards. The standard deviation for yards gained was 385.46. The standard deviation for yards allowed was 447.15. Iowa gained 2917 yards in conference play and allowed 2452 Their offensive SDPI was 0.27 = ([2917-2813.64]/385.46). Their defensive SDPI was 0.81 = ([2813.64-2452]/447.15). Their total SDPI was 1.08 which ranked 4th in the conference.

To refresh your memory, here are the 2008 Big 10 Standings.

Now here are the 2008 SDPI Standings sorted by total SDPI, with conference rank in offense, defense, and total SDPI in parentheses.

Penn State was clearly the best team in the Big 10 last season, posting the second best offense and number one defense in the conference. However, what really jumps out, at least to me, is the high finishes by both Illinois and Wisconsin. According to SDPI, the Illini and Badgers, who both finished 3-5 in conference play, were among the top three teams in the Big 10 in terms of performance on a down-to-down basis. However, that performance did not translate to achievement on the scoreboard. Illinois finished first in the Big 10 in yards gained, but only fourth in points scored thanks a defense that rarely gave the offense good field position by forcing turnovers (last in forced turnovers with 12 in conference play) and a special teams unit that ranked 93rd nationally in punt return average and 63rd in kickoff return average. Meanwhile, Wisconsin saw a disconnect on the other side of the ball. Their defense ranked a respectable fourth in the conference in yards allowed, but a deplorable ninth in points allowed. The offense contributed to the poor showing of the defense by leading the conference with 22 turnovers. Opposing Big 10 kickers also torched the Badgers, making all 13 of their field goal tries. Further down the standings, we see that Minnesota, despite their bowl appearance after a winless conference campaign, still has a long way to go to achieve mediocrity and that Michigan was very bad last season.

Best Offense: Illinois 1.57
The Illini moved the ball well against everyone. They topped 500 yards of offense three times in league play, but amazingly lost one of those games (Minnesota) thanks to three turnovers.

Worst Offense: Minnesota -1.46
Remember the Glen Mason era, when the Gophers could pound the ball with the best of 'em? Minnesota cracked the 100-yard rushing barrier in just two conference games, and averaged only 78 yards per game and 2.56 yards per rush in conference play, easily the worst in the Big 10.

Best Defense: Penn State 1.20
Until Southern Cal dismantled them in the Rose Bowl, this really looked like one of the best defensive units in the nation. Only three conference foes eclipsed the 300-yard mark, and only Illinois was within sniffing distance of 400 yards (372).

Worst Defense: Indiana -2.14
The Hoosiers were definitely the anti-Penn State. Only two Big 10 teams failed to gain at least 400 yards against the Hoosiers woeful defense.

Hardest Schedule (based on cumulative SDPI of opponents): Indiana 4.55
Believe me, this is the only spot where the Hoosiers have a shot at finishing number one. The Hoosiers faced eight of the top nine teams in the Big 10, and the only way the schedule could have been more difficult would have been to swap in Ohio State for Minnesota. Of course, it also helps that the Hoosiers had no way of playing themselves as they were easily the worst team in the conference.

Easiest Schedule (based on cumulative SDPI of opponents): Purdue -4.02
The schedule was set up to send Joe Tiller out a winner, but fate (and poor special teams which we'll get to later) intervened. Purdue played the three worst teams in the conference (Minnesota, Michigan, and Indiana), and not surprisingly, their two conference wins happened to come in those games.

Entire Schedule Strength (hardest to easiest)
Indiana 4.55
Michigan 4.43
Ohio State 1.29
Michigan State 1.06
Minnesota 0.43
Iowa 0.13
Penn State -0.15
Illinois -1.84
Wisconsin -2.16
Northwestern -3.80
Purdue -4.02

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

Ohio State
I know statistically the Buckeyes were only fifth in SDPI, and this was likely the worst Buckeye team since 2004. However, Ohio State was one Terrelle Pryor fumble from winning their third straight outright Big 10 title and playing in the Rose Bowl. Pryor put up good numbers as a true freshman, rushing for over 600 yards and posting a passer rating of 145.62, which would have ranked 21st in the nation if he had enough attempts to qualify. Pryor should improve in 2009, and even if he never achieves the zenith most recruiting gurus think he will, he is an obvious upgrade over Todd Boeckman. Next season, the Buckeyes must play the four teams that finished above them in SDPI (Penn State, Illinois, Wisconsin, and Iowa). Each of those teams save Penn State must travel to Columbus. And speaking of Penn State, while the Lions were clearly the best team in 2008, attrition will likely prevent them from being the best team in 2009. The Lions will be breaking in a new quarterback to replace departing senior Daryll Clark. The Lions will also be without their top three receivers from 2008 and three of their top five tacklers. Winning in State College will be no gimme for the Buckeyes in 2009, but Penn State will likely find themselves on the wrong end of a few conference games as well.

The team(s) you should be buying are...

Illinois, Purdue, and Wisconsin
I discussed earlier how on a down-to-down basis the Illini were the second best team in the Big 10 last season. But as they say, a picture is worth a thousand words. See if you can guess from the table below during which season Illinois went to the Rose Bowl and during which season they missed a bowl game entirely. As you've probably already guessed, the more statistically dominant season is the one where the Illini did not make it to postseason play. The biggest difference between the six win conference season of 2007 and the three win conference season of 2008 is turnovers and random chance. The Illini were +7 (second in the Big 10) in turnover margin in conference play in 2007 and 3-1 in one-score conference games. In 2008, they were -4 (eighth in the Big 10) in turnover margin in conference play and 1-1 in one-score conference games. Both those trends have a good chance of reversing themselves in 2009 and the Illini should return to a bowl game. Another team that was better than their record indicated in 2008 was the Purdue Boilermakers. In Joe Tiller's swan song, Purdue performed from down-to-down at about their usual rate. They were fifth in the conference in offense and fifth in defense. Unfortunately, their punt coverage units let them down. Purdue gave up three punt return touchdowns on the season (two in conference play) and was dead last in the nation (120th) at covering punts, allowing 16.7 yards per return. That's not to say Purdue was unlucky in covering punts, they were plain bad, but performance in special teams is not as consistent year-to-year as performance on offense and defense. That's great news for new head coach Danny Hope and all Purdue fans. One area where Purdue was exceptionally unlucky was at recovering their own fumbles. Purdue fumbled only 12 times in 2008 (tied for sixth in the nation for fewest fumbles), but were only able to fall on two of them. Purdue was last in the nation in percentage of own fumbles recovered. Unlike special teams, fumble recovery is totally random, so you can bet Purdue will have better luck corralling loose balls next season. With better special teams play, some improved luck, and a competent quarterback under center, Purdue should be back to a mid-level bowl game next season. We've already touched on some of the reasons Wisconsin is poised for a rebound in 2009, but another factor to add to the equation is their poor luck in close games in 2008. Wisconsin was involved in four one-score Big 10 games in 2008, and was victorious in only one. The Badgers lost by two points to Michigan, three points to Ohio State, and by a single point to Michigan State. Their luck in close games should improve and if quarterback Dustin Sherer makes any progress in his senior season, the Badgers could be a darkhorse contender for the Big 10 title.

The team(s) you should be selling are...

Michigan State and Minnesota
After posting much better numbers than their 3-5 conference record would indicate in 2007, the Spartans reversed course and finished well above where a team with their middling numbers should hae been expected. The Spartans went 6-2 in the Big 10 despite being outgained by about 36 yards per game in conference play. Their offense, despite the presence of Javon Ringer was the eighth best in the conference, and the defense was also eighth in yards allowed. So how did Michigan State manage to win all those games? For starters they were 2-0 in one-score games. Their one-score games also happened to occur against Iowa and Wisconsin, two of the better teams on the schedule. Their turnover margin was another reason for their success. While they were only -1 for the season in conference play (sixth in the Big 10), once we remove their two blowout losses to Ohio State and Penn State, that margin jumps to +6. The only other conference game in which they had a negative turnover margin was against Purdue. Michigan State was already outclassed against the Buckeyes and Lions, so the turnovers merely served to make their beatings more embarrassing. However, against teams of similar or less ilk (Indiana, Iowa, Northwestern, Michigan, and Wisconsin), the extra turnovers allowed the Spartans to win despite their failings on a down-to-down basis. In 2009, the Spartans will be breaking in a brand new backfield as both Ringer and quarterback Brian Hoyer have exhausted their eligibility. The offense, which wasn't that good to begin with, will probably remain near the bottom of the conference. The defense will likely see some improvement as four of the top five tacklers return as does the best playmaker on the line, defensive end Trevor Anderson. The Spartans luck will likely find some balance between their devine providence in 2008 and their poor fortune in 2007. Expect their conference record to strike some counterbalance between 2007 and 2008 as well, but the Spartans are by no means Rose Bowl contenders. Until November, it looked like the Golden Gophers had turned the proverbial corner. At the end of October, they were 7-1 (3-1) in the Big 10, and memories of a winless conference season in 2007 were forgotten. Then the Gophers dropped their last four conference games and were bludgeoned by Kansas in their bowl game. What happened? The turnovers stopped coming. To be fair, Minnesota did not play as well on offense or defense over their last four conference games, but being outgained on average by about 62 yards per game is not the mark of a team that wins 75% of its games. All told, Minnesota was last in the conference in offense and ninth in defense. The offense has a great chance at improving with players such as quarterback Adam Weber and receiver Eric Decker, but the Gophers have a long way to go on both sides of the ball to be average.

The team(s) you should be holding are...

Michigan
Yes Michigan really was that bad in 2008. Only Minnesota posted a worse offense, and only Indiana performed worse on defense. Michigan has a long way to go to get back to where they were, but unlike Minnesota and Indiana, they have a brand name, and a proven coach. Rich Rod's first team at West Virginia went only 3-8. His next six teams never won fewer than eight games. Michigan may well miss out on a bowl once again in 2009, but in the long run, Rich Rod will right the program.

2 Comments:

Anonymous Brandon said...

Fun analysis, pretty interesting about Wisconsin and Illinois faring so well.

One thing about Penn State, they do loose their top three receivers, but they are NOT breaking in a new quarterback. Darryl Clark will be the quarterback for the upcoming season.

11:41 AM  
Blogger matt said...

Good catch. Clark is returning. My 2008 preview mags listed him as a senior as did cfbstats.com. Good news for the Lions.

5:25 PM  

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