NFL statistics get a bad wrap. No, football will never be baseball. Sundays are never going to primarily consist of discrete, easy-to-measure events that readily allow us to assign full credit and blame (though that hasn't stopped us from trying!). And no, the contents of a spreadsheet is never going to tell us everything we need to know about what happens on a football field. But why does it have to?
Can't statistics help us make sense of the NFL world without having to paint the complete picture? Watching film is an irreplaceable part of evaluating NFL teams, but it sure as hell does't work 100 percent of the time. If you need evidence of that look no further than the NFL Draft, where scouting heavily influences the selection of players and team success rates resemble batting averages. You need both and anyone that tells you otherwise is in denial.
The key is using statistics correctly and putting them in the proper context. At the team level, there are several concepts that can tells a good amount about what we should expect from that team in the future. In the past few years, Bill Barnwell has put together some excellent primers at Grantland on some of the more useful statistical concepts that can help us predict a team's performance in the coming NFL season. I'm going to use those concepts to see what we can learn about the 49ers going forward and while some basic explanation will be involved, I highly recommend you check out Barnwell's articles if you want to know more about the why behind them.
It's one of the most basic statistical rules of thumb in sports: point differential is a better predictor of future performance than a team's win-loss record. The logic behind this is straightforward. Teams have the possibility to score—or allow—points on every single play compared with only 16 opportunities to win or lose a game. This expanded sample gives us more chances to evaluate a team and provides us with a more accurate representation of a team's true performance level.
How does this help us predict the coming season? In general, teams that win more games than you would expect based on their point differential (this expected winning percentage based on point differential is called their Pythagorean expectation) tend to decline the following season while teams that win fewer games than expected tend to improve.
For the second consecutive season the 49ers finished with an actual win-loss record that was within a half-game of their Pythagorean expectation, indicating that their 12-4 record was on par with what we'd expect given their point differential. San Francisco outscored their opponents by an average of 8.4 points per game in 2013 giving them the league's third best point differential, trailing only the two eventual Super Bowl participants in Denver and Seattle.
Many of you might be saying, "I didn't need you to tell me this to know that the 49ers were a legitimate 12-win team," and I wouldn't argue with you. But consider this the first of several pieces of evidence to support that claim.
Record in Close Games
Closely tied to the premise that point differential is a better predictor than win-loss record is how a team performs in one-score games. While TV pundits will tell you winning close games comes down to heart, some mythical clutch gene or simply wanting it more, the reality is that the outcome of one-score games in the NFL is often decided by just a few plays. A phantom roughing the passer penalty. A receiver that trips coming out of his break, turning a reception into a turnover. A muffed punt that sets up a game-winning field goal.
These are important plays in any game. But in one-score games, they are often the difference between a win and a loss. Does the outcome of these few plays really tell us more about a team than the other 120 plays that happened throughout the game? Not at all. Which is why teams that win a high percentage of their one-score games—something that is almost impossible to do over the long-term—tend to give a few of those games back the following season.
Great teams don't separate themselves by finding ways to pull out close victories; they do it by avoiding them altogether, which is exactly what San Francisco did last season. The 49ers played in just five games decided by a touchdown or less, going 3-2 in those contests. Only Philadelphia (3-1) and St. Louis (1-3) played in fewer one-score games. Of those five games, four of them came against eventual playoff teams (Green Bay, Carolina, New Orleans, Seattle) while the fifth came on the road against Arizona, a division rival that happened to win 10 games last season.
On the other end of the spectrum, only Denver managed to best San Francisco's nine wins by double digits. When the 49ers faced inferior competition—of those nine games, six of them came against teams that finished in the bottom half of the league in DVOA—they dominated.
Winning the turnover battle creates extra opportunities for your offense to put points on the board while simultaneously taking away a scoring chance from your opponent. The problem is turnovers tend to be inconsistent from year to year. Dropped interceptions, tipped balls and the randomness of fumble recoveries all contribute to this inconsistency. Because of it, teams that find themselves on the extreme ends of the turnover margin rankings tend not to stay there for very long.
For an example of this, we don't have to look far. In 2011, the 49ers finished the season with a league-best plus-28 turnover margin; the following season they finished with a turnover margin of plus-9. That's still very good, but it's nowhere near that unsustainable mark from 2011.
In 2013, San Francisco again found themselves among the league's best with a turnover margin of plus-12, tying Philadelphia for the fourth-best differential in the NFL. While the 49ers have come back down to earth in this area since their historically good 2011 campaign, they have now found themselves with a top 10 turnover margin for three consecutive seasons. How have they managed to remain consistently good in a historically inconsistent category?
Over the past three seasons, the 49ers' offense has fumbled the ball—not necessarily lost, but just put the ball on the ground—at an almost exactly league average rate. In that same time frame, they've forced turnovers at a rate over league average, but not unusually so and that number is propped up a good amount by the league-leading 38 turnovers they forced during the 2011 season. San Francisco's fumble recovery rate on all available fumbles also hasn't veered far from the league average during that time.
It turns out that San Francisco's turnover prowess is driven primarily by their incredibly low interception rate. Between Colin Kaepernick and Alex Smith, the 49ers have posted an interception rate below two percent in every season with Harbaugh at the helm. To put that feat into context, Aaron Rodgers and Tom Brady currently sit atop the career interception rate leaders and neither player has ever put together three straight seasons under two percent.
A lot of this can be credited to a hyper-conservative offense that has emphasized checking down, throwing the ball away or even taking a sack in situations (such as third-and-long) where most teams would be more willing to take a chance into coverage downfield. However, this will be a big area to keep an eye on during the coming season. With an improved receiving corps and another year of development for Kaepernick, many are expecting the 49ers to throw the ball more frequently in 2014. If that happens, Kaepernick is almost certainly going to turn the ball over at a higher rate. The 49ers can withstand a modest increase and remain in good shape. But if that increase becomes more significant or gets paired with poor fumble luck, it could be enough to cost the team an extra game or two that it might have otherwise won.
I wrote about injuries as they relate to the 49ers more in-depth back in March following the release of Football Outsiders' Adjusted Games Lost data, so I encourage you to check that out if you haven't already.
In short, injuries tend to regress to the mean from one season to the next—with a few exceptions—and last season the 49ers suffered a lot of them. After finishing as one of the league's healthiest teams for five straight seasons, the 49ers suffered a flood of injuries in 2013. San Francisco's AGL jumped 68 games from 2012 to 2013, which is the third largest increase in FO's database. Though the 49ers are off to a poor start in this area with the expected absence of linebacker NaVorro Bowman for the first half of the season, they should get some of those games back in 2014, especially on the defensive side of the ball.
No single element will ever tell us everything that we need to know about the NFL and its teams. Statistics are no different, they're only a piece of the puzzle. I'm a firm believer that the intelligent use of statistics merged with thorough film study provides the most comprehensive view of a team, but even then it's a murky view at best. History may tell us that the 49ers are primed for a healthier season in 2014, but they could end up in the minority of teams with back-to-back unfortunate seasons. Such is life in the randomness that is a 16-game NFL season. So rather than taking these concepts as rules that cannot possibly be broken and cursing the use of statistics forever when they're wrong, remember that our eyes lie to us all the time. These concepts are only there to help straighten out some of that randomness and point us in the right direction.
Having said that, San Francisco's underlying performance matches up with what their aggregate win-loss record tells us; they're one of the league's best teams and are primed to remain there for the foreseeable future. With that mystery solved, I'll be checking back in the coming week to see what these concepts can tell us about San Francisco's opponents in the 2014 season.