Statistics on San Francisco's Slow Offensive Starts (And Why You Shouldn't Worry)

So you may have noticed that San Francisco's offense was practically the walking dead to start their playoff games this year. If not, here's a reminder of what they did on their opening drives. Against Green Bay, Colin Kaepernick threw a pick-six (pictured above). Against Atlanta, they gained only one yard in the midst of a three-and-out. And against Baltimore, another three-and-out featured an inexplicable illegal formation on the first play of the game. All told, the 49ers offense scored zero points, amassing only 23 yards on 10 plays. And thanks to an almost equally zombified defense, they found themselves down by a combined score of 31-10 at the end of the first quarter. Good thing the NFL rule book allowed for (at least) three more.

What you might not have noticed is that this phenomenon of slow starts wasn't at all atypical of how the offense opened games during the regular season. Or maybe I'm projecting here, and it turns out I'm the only one who didn't notice. Thankfully, David brought it to my attention, and asked me to see whether or not the stats agreed with what his (potentially lyin') eyes saw. That's exactly what I'll lay out in the rest of this relatively brief post (for me).

At Football Outsiders, we have a whole page dedicated to drive stats, which are put together each week by Jim Armstrong. You can click on that link to see how the 49ers did over the course of the season on their own drives, the ones they had to defend, and the net difference between the two. Jim was kind enough to send me his drive-by-drive data, which I was able to examine alongside the play-by-play database we use to calculate our efficiency metric, Defense-Adjusted Value Over Average (explained in detail here). Interestingly -- and this wasn't really my expectation going in -- viewing these two data sources side by side does a good job of illuminating why San Francisco's opening drives seemed to look so bad.

Here's a table with all the important stats for each team's first offensive possession in regular season games:

To situate ourselves, "LOS" is average starting field position, "Plays" is average number of offensive plays, "Pts" is average number of points scored, "DSR" is a measure of drive success that Jim created (explained here), "Y/P" is average yards per offensive play, and "DVOA" is, as I just said, Football Outsiders' measure of play-by-play efficiency.

According to the drive-by-drive stats (i.e., Plays, Pts, and DSR), San Francisco's offense was indeed pretty abysmal on their 16 opening drives. They ran over one play fewer than the average NFL offense, they scored half as many points, and their DSR says they were about 10 percent less likely than the rest of the league to get a first down or touchdown in a given series of downs.

So a dark, dark picture emerges if you look at opening drives in their entirety. The interesting thing is that the picture gets much brighter if you instead look at individual plays during those opening drives. That's what the final two columns are measuring. According to Y/P and DVOA, it turns out that, on a play-by-play basis, the 49ers' offense was actually right around the league average during their opening possessions.

Why the difference? Naturally, it's because San Francisco's offense had a bunch of successful individual plays during their opening drives, but those plays didn't result in many first downs or touchdowns when all was said and done. (It's not really relevant to the discussion, so I'll set aside the fact that DVOA is the only one of the stats in the table that adjusts for opponent and game situation.) For instance, while only two of San Francisco's 16 opening drives went the distance, those two drives averaged over 10.0 Y/P, and three other non-touchdown drives averaged over 6.0 Y/P. Basically, when they had good plays, they were really good, but when they had bad plays, they were really bad; and that even's out in the play-level stats. In the drive-level stats, however, all that matters is that there were more bad plays, which led to fewer scores.

Taking an even closer look at those play-level stats, we additionally find that the main reason for the 49ers boom-or-bust tendency on opening drives was a huge divergence based on the down. On 34 first downs, they averaged a fifth-best 6.2 Y/P and had a third-best DVOA of 42.7%. On 26 second downs, they were closer to the league average: 19th in Y/P (4.8) and 21st in DVOA (3.2%). And on 19 third downs during opening possessions, the 49ers offense got even worse, ranking 23rd in both Y/P (4.3) and DVOA (-25.1%).

So you want the elevator pitch for why the offense seemed to suck on their first drives? Here it is: They had moderate-to-large gains on first downs, but stalled on second downs and third downs, and that made it extremely difficult to turn those drives into points.

But here's the good news: I'm skeptical about how predictive any of this is for 2013 -- for a few reasons. First, we know that larger sample sizes are better for evaluating teams than smaller sample sizes, and 16 opening drives or 79 offensive plays during those drives -- tied with Chicago for the fewest in the league I might add -- are really small sample sizes. Over the course of 959 total plays during the regular season, San Francisco had the fifth-most efficient offense in the NFL. I'll put my money on that being the more reliable predictor.

Similarly, we know from previous Football Outsiders research that third down performance doesn't carry over from one season to the next. Like turnovers and red zone efficiency, it's a stat that's better for explaining past results than predicting future results. What's more, the best down for predicting how good an offense is going to be the following year is first down, precisely the one San Francisco excelled at in their opening drives of 2012; and over the entire sample of offensive plays for the season, they ranked No. 1 in first down DVOA. Either way you slice it, it's much more likely that they'll continue to be good on first downs next season than that they'll continue to be horrible on third downs during opening drives.

Finally, there's the one column in the table I haven't discussed yet: average starting field position. The 49ers' return units ranked in the middle of the pack this season, which showed up in LOS for their opening drives because all 16 of those drives began after a kickoff or punt. Leaguewide, 21 different teams had at least one initial offensive possession come via an interception, fumble recovery, or missed field goal; San Francisco wasn't so lucky. And the best part is that, like third downs, special teams performance is also notorious for not carrying over from one year to the next (See Akers, David). Sure, that lack of carryover means this year's mediocre stats for return teams might get significantly worse in 2013, but there's just as much of a chance they'll get significantly better. If so, San Francisco's opening drive stats would get better simply because any team is more likely to reach the end zone if they have a shorter distance to traverse.

Now, as I'm wont to do, we must acknowledge that the stats only take you so far. A much deeper analysis of things like game film and offensive play-calling tendencies would probably shed more light on the 49ers' lack of success on opening drives in 2012. After all, I have a nagging concern about why an otherwise-explosive offense would be so unproductive in drives that, for all intents and purposes, were scripted. Given the veritable wizardry of the current coaching staff, I can't imagine that overall game-planning is the problem; their scripting might be, though. I encourage any intrepid Niners Nation reader who is savvy about X's and O's to take up that cause.

So we know what the stats say about San Francisco's slow starts on offense. Let's hear your theories in the comments section. And if you have any requests for specific opening drive stats that I didn't mention, feel free to ask. I've got a ton of data at my disposal over here.