Two Interesting Findings

Dr. X posts this from the NFL Statistical Service in Vatican City:

"As we get warmed up for the final leg of the NFL season, I wanted to report on two interesting findings. Both studies had the same catalyst - what with the 49ers breathing down our necks, I had to wonder - just how good are these guys?

"One study made me feel better, the other made me feel worse.

"First the good news. Much has been made of the fact that the Seahawks have gotten this far despite being outscored by their opponents this season. The differential is 16 points. And this is a concern, because teams that have records that are incongruent with their point differentials are candidates for (all together now)...mean regression.

"The good news is that, if Seattle has the sniffles, San Francisco has double pneumonia. No team in the NFL has been so badly outscored by its opponents. San Francisco's opponents have scored 83 more points than the 49ers, despite SF having a pretty good offense. The defense has gotten its act together a bit the last three games, but SF gets blown out by good teams. And once Seattle has its quarterback and running back, er...back, the SF defense will be chum in the water when they come to town.

"But there is also bad news. Given the field days Grossman and Huard had against them, I wondered if the 49ers had the worst pass defense in the league. To assess this I ran defensive IAYPAs (DIAYPA) for all NFL teams. This is a pretty good statistic. You won't necessarily be an elite team just because you have a great pass defense, but it helps: the average winning percentage of the top 5 DIAYPA teams is .560. The Bears and Ravens are #1 and #2 in DIAYPA and are 9-1 and 8-2, respectively. And if you have a really bad pass defense you will be living in the cellar. The bottom five DIAYPA teams have an average winning percentage of 0.300.

"San Francisco is not the worst, however - they're not even in the bottom five. Here are the bottom five teams, with DIAYPA and winning percentages:

• Washington (7.3) - 0.300
• Detroit (6.2) - 0.200
• Houston (6.1) - 0.300
• Green Bay (5.9) - 0.400
• Tampa Bay (5.9) - 0.300
  

"Four of these five teams are either last or tied for last in their division (Green Bay is the only exception).

"San Francisco is bad, of course, posting a DIAYPA of 5.5, 1/2 standard deviation above the NFL average of 4.9. But so is Seattle, with almost exactly the same numbers. The composition is a bit different though - San Francisco gives up more yards per attempt, but has gotten more interceptions so far (9 vs. 6 for Seattle).

"So, returning to the question - it's hard to argue that Seattle's defense is better than San Francisco's. The passing numbers look about the same. And San Francisco has actually given up fewer yards per rush (4.2) than the Seahawks (4.5) this year.

"On the other side of the ball, San Francisco has an excellent offense with an improving young quarterback, good receivers, and a future All-Pro running back in Frank Gore (2nd in the League with 1043 yards this year).

"Gore is a monster, but he has a weakness: he has fumbled five times, more than any other running back this year. And the fumbles have been costly - all have been recovered by the other team. If we impute a 50 yard penalty for each fumble, Gore's fumble-adjusted yardage would be 793 yards - still fine, but more Ronnie Brown than Tiki Barber.

"So how serious is the 49er challenge? Well, San Francisco has to go on the road against two good teams - the Rams and the Saints. Seattle stays at home against Green Bay, then goes to Denver. I'd guess Seattle picks up a game out of that. Then both teams play patsies - Seattle goes to Arizona and Green Bay visits SF.

"And then, on December 14th, SF comes to Seattle for a Thursday night game. I'm sticking with my 28-0 prediction for now."