Nate Silver notes that 14 of the 20 best Super Bowl defenses, according to the simple rating system at pro-football-reference.com, have won the big game, while the 20 best offenses have gone 10 for 20.

This isn’t exactly a revelation in terms of who has won titles. Teams with bad offenses rarely make the postseason. There is far more variation in offensive numbers than defensive, and this weeds out the horrible offenses. By the time the playoffs roll around, it’s a contest between “good enough to great” offenses, and the quality of the defenses becomes more variable.

I wanted to go a bit more granular, though, and look at each year and the offensive and defensive ratings of the Super Bowl teams. I will note that the SRS on offense and defense has some cross-over contributions. A good ball control offense can help prevent points, while an aggressive defense can help create them with field position. So, when we are comparing offensive and defensive ratings, we are really comparing point creation and point prevention, however the team accomplishes it.

When teams have had the better overall rating, and both a better offensive and defensive rating, they are 17-7 in the Super Bowl.

When a team has the better overall rating and offensive rating, but the opponent rates higher defensively, they are only 4-6 in the Super Bowl. When a team is rated better both overall and defensively, but not offensively, they are 6-5. (There is one case where teams had the exact same overall rating (Washington-Denver)).

If we look at defensive rating, then, the “better” team went 30-16 in the Super Bowl, while the “better” offensive team went 26-20 (Remember, there were 24 times a team rated as both). Upsets are more likely when the underdog is better on one side of the ball, though we have seen some notable ones in the last decade where one team appeared stronger all around.

Silver also points out that while Baltimore has a reputation for defense, San Francisco was much better this year (ranking as the 17th best for a Super Bowl team by defensive SRS), and is also better offensively. This would seem to suggest San Francisco as a heavy favorite.

The regular season SRS has them at 7.2 points better. The line opened at 5, but has moved down to 3.5 with the betting public heavy on Baltimore. What happens when the SRS differs greatly from the Super Bowl point spread? Well, remember that it is a “simple” rating that doesn’t know things like injuries, changes, and recent performance. It also does not include post-season results at all.

There have been 23 Super Bowls where the difference between the point spread and SRS difference between teams was at least 4 points. If you had gone in the direction of the SRS when their was a significant difference, you would have gone 8-15. It is good information to have, but in the crucible of the Super Bowl, everything is analyzed and examined and considered.

In this case, the difference is accounted by the following things:

1) It doesn’t include the postseason. Baltimore just won two games on the road against highly rated teams as large underdogs. Thus, the SRS is undervaluing them, since those results are not included. Compare it to the basketball NCAA Tournament. When a team gets big wins over quality opponents, it improves their profile dramatically in early March. We aren’t including those games in regular season SRS, but Baltimore is really 13-6 with 2 high quality road wins not accounted for.

San Francisco, of course, won two games to get here also, but those results were more in line with previous expectations and would not change their rating as much.

2) Baltimore’s offense with Jim Caldwell at offensive coordinator. It has been better. Will it continue? One has to account for the possibility.

3) Baltimore’s defense is healthier than it was. Terrell Suggs missed half a year and was still getting healthy. Ray Lewis was out. They had to work around the loss of Ladarius Webb. The regular season probably understates the Ravens’ defense, which leads to . . .

4) Baltimore has been a perennial contender. Baltimore’s SRS is 2.9 for the regular season. For the previous four years, though, they were never below a +6.0. If you consider that the results of a 16 game schedule are still a small sample and may not reflect true value, then the Ravens are better than your typical +2.9 team. That’s even before we consider what they did since the end of the regular season.

San Francisco is favored, and SRS says they are much better. In this case, though, it is closer than that. San Francisco is a legitimate Super Bowl caliber winning team, but Baltimore also has to be considered top 5 based on how they have played recently coupled with their history of being among the best teams. I’m still weighing my pick, but it’s not as clear cut as just looking at the power ratings from the regular season.

[photo via USA Today Sports Images]