There's a common idea that someone can make statistics say just about anything. In the world of professional sports, statistics are a key instrument, and in fact are one of the reasons many of us love sports like we do. The last few years has seen a rise in alternative looks at sports statistics, particularly in baseball and football through Baseball Prospectus and Football Outsiders, respectively. These sites look at new ways to assess the performance of players and teams and give us a better idea of how good or bad a team truly is.
Prior to the advent of these type of sites, the general way we have looked at, and most continue to look at, NFL teams is through the yards per game statistics. According to those stats, the 49ers rank 18th in rushing offense, 18th in passing offense and 21st in total offense. On defense the 49ers rank 23rd in rushing defense, 19th in passing defense and tied for 21st in overall defense.
Over at Football Outsiders, they use a variety of statistics, but I thought we'd just look at DVOA for now. Sort of take it one bite at a time. Here's an overall rundown of all their new statistics, but I'll give the quick and dirty explanation they use:
DVOA is a method of evaluating teams, units, or players. It takes every single play during the NFL season and compares each one to a league-average baseline based on situation. DVOA measures not just yardage, but yardage towards a first down: five yards on 3rd-and-4 are worth more than five yards on 1st-and-10 and much more than five yards on 3rd-and-12. Red zone plays are worth more than other plays. Performance is also adjusted for the quality of the opponent. DVOA is a percentage, so a team with a DVOA of 10.0% is 10 percent better than the average team, and a quarterback with a DVOA of -20.0% is 20 percent worse than the average quarterback. Because DVOA measures scoring, defenses are better when they are negative.
I'm introducing these stats now because as I've mentioned in the past, I'd like to use them a little more often. It's taken time to do that but once again, I hope we can do that.
Through week 5, Football Outsiders ranks the 49ers 26th in passing offense, 12th in rushing offense and 26th in overall offense. Overall it's not a dramatic change from the traditional stats, but the difference can be seen in the rushing and passing offense. The 49ers passing offense DVOA is -18.3%, while there rushing game is 0.6%. 0% always represents league average and on offense, positive is better.
On defense, FO ranks the 49ers 8th against the pass, 24th against the run and 11th in overall defense. Clearly this differs quite dramatically as compared to the traditional stats. In this case, the 49ers passing defense DVOA is -13.1%, while there rushing defense is 9.1%. Since defense is the inverse of offense, a negative number is better (0% is still league average).
Initially I was thrown off by the particularly high passing defensive rank. I can't even begin to look at everything they consider, but looking at the first 5 box scores, if you throw out the Saints game, the 49ers pass defense hasn't exactly been shredded in the traditional sense. Randy Moss had his big play, Cassel got some yards in the mix, Boldin had a big second half. However, in reality, the rushing defense is what killed the 49ers.
Traditional stats rank the 49ers 19th in passing defense, while FO ranks them 8th. In traditional yards per game stats, a 15 yard pass on 3rd and 20 has the same value as a 15 yard pass on 3rd and 10. This exact type of play happened in the Patriots game leading to that last Pats field goal. On 3rd and 20 the Patriots completed a 13 yard pass. DVOA would not value that completion at the same level as passing yards per game and that is reflected in a higher pass ranking by Football Outsiders.
Now this doesn't mean that I'm trying to argue that the 49ers pass defense is better than it is. It's clearly struggling, but I think this shows how much bigger a concern the rush defense should be. Hopefully this makes some modicum of sense. It took me some time to break it down in my head and I'm probably still mis-speaking in certain areas. Feel free to share your own thoughts.