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Digging deeper into the 49ers' run-pass ratio

The 49ers are widely considered to be one of the most run-heavy teams in the NFL. Using data from Football Perspective, we delve a bit deeper into that notion and consider what that might mean for San Francisco's run/pass ratio next season.

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Who is the most run-heavy team in the NFL? Ask this question to most any self-respecting NFL fan and chances are the San Francisco 49ers will be one of the first teams mentioned. Since taking over as the team's head coach in 2011, Jim Harbaugh has established an offensive identity that is based around a physical, smash-mouth style of play that relies heavily on Frank Gore and the running game.

Over the course of the last three seasons, no team has piled up more rushing attempts than the 49ers. In 2013, San Francisco was one of only two teams to run the ball on more than half of their plays, throwing the ball on a league-low 47.7 percent of offensive plays. But are these raw rushing totals really enough to tell us that the 49ers lean more heavily on the running game than the other teams in the league? Not quite. While no one is confusing the 49ers offense with Peyton Manning's Denver Broncos, there's a little more to the story than simply pulling up rushing totals and calling it a day.

The other important thing to consider when attempting to find a team's true run/pass ratio is the game situation. Teams playing with a lead are going to be more likely to run in order to kill clock while teams who are trailing are going to be more likely to pass to catch up. This simple truth is the reason why cumulative statistics can often be misleading, which is the situation we find ourselves in when looking at San Francisco's total rushing attempts.

With a regular season winning percentage of 0.760 since 2011, the 49ers have spent a good chunk of time playing with the lead over the past three seasons. Inevitably, this is going to skew San Francisco's true run/pass ratio. The question, of course, is by how much? Lucky for us, Chase Stuart of Football Perspective has devised a metric that can help answer that question. Game Scripts tells us the average points differential for a team at any time of each game, giving us an indication of which teams spent the most time playing with a lead as well as the magnitude of that lead.

Using last season's results as an example, the 49ers had an average Game Script of 5.9 points. This tells us that at any moment during a game last season, on average, San Francisco held a lead of 5.9 points over their opponent. That mark was good enough for the second highest in the NFL, trailing only the Broncos. Using this information, we can now revisit our run/pass ratio and attempt to negate the effect of the game situation on the play-calling.

To do so, it gets a little mathy. So if you're interested in learning more on the methods of how this data was derived I encourage you to check out Stuart's explanation.

By using Game Scripts in conjunction with a team's run/pass ratio we get what Stuart calls Pass Identity. Simply, Pass Identity tells how pass happy (or run happy, depending on your perspective) a team was relative to league average while taking into account the score of the game.

Remember that league-low pass percentage of 47.7 percent? Looking at that number through the scope of Pass Identity turns the 49ers from the most run-heavy offense in the league to the 13th most run-heavy offense. What does this tell us? It means that when the scoreboard isn't dictating otherwise, the 49ers are throwing the ball at nearly a league-average rate. This is quite the departure from what conventional wisdom would lead us to believe.

If we think about how the typical 49ers game went in 2013, this makes a lot of sense. As Stuart points out, San Francisco had the league's best points differential through two quarters and three quarters last season. That led to a lot of fourth quarters spent running to preserve a lead and grind out the clock. In fact, no team had more fourth quarter rushing attempts than the 49ers did last season.

So what's the point of looking at all this data? Beyond simply being interesting, a hot topic in Ninerland this offseason has been whether the 49ers are going to put the ball in the air more frequently in 2014. Colin Kaepernick is entering his fourth season in Harbaugh's system and his second full season as a starter. The offensive weapons Kaepernick has at his disposal—assuming everyone remains healthy—have never been better. It would be very reasonable to expect San Francisco to throw the ball more in the upcoming season. But if that does in fact happen, it's more likely that the cause of the uptick in passing attempts is due to playing in more tightly contested games than some shift in offensive philosophy.

When the outcome of the game is still in question, Harbaugh is already throwing the ball at roughly a league-average rate. Given what we know about him and the style of play he seems to prefer, is there any reason we should expect the frequency of pass plays to increase significantly? As much as I would like to see otherwise, I'm inclined to think the answer is likely no.