Quarterback sacks, and the story that they tell, plays a role in this year’s Super Bowl participants. That role is decidedly different for each of the two teams. One made a bold switch at the quarterback position. The other has a quarterback coming of age and maturing in an area where many of his contemporaries have not, while making a bold switch at offensive coordinator.

A couple of years ago, I wrote about teams changing quarterbacks during a season and what rate stats stay most and least consistent. (I also looked at quarterbacks changing teams). The summary is this: the two most consistent statistical traits for quarterbacks are their sack rate and completion percentage. The rate at which a quarterback takes sacks is the most consistent thing when a passer changes teams. It is the least consistent when a team changes quarterbacks. Contrary to common wisdom, interceptions are far more random than many want to believe, while avoiding sacks is a skill that tends to persist for a quarterback.

Let’s turn first to the San Francisco 49ers. When you look at the quarterback switch made by Jim Harbaugh, it reinforces those elements. Alex Smith and Colin Kaepernick had the exact same number of pass attempts, and put up somewhat similar overall results, though how they got their differed. Kaepernick had the superior YPA, though both were above 8.0 and much better than the league average. Smith had the much better completion percentage, and threw a higher percentage of touchdown passes. Both were good at avoiding interceptions, though Kaepernick was better.

When it comes to sacks, though, Kaepernick was a clear improvement, and it touches on the one criticism I had of Alex Smith the last two years. He was too cautious at times and held the ball too long. No game was that a bigger issue than last year’s Harbaugh Bowl, when Alex Smith was sacked 9 times, and San Francisco managed only 12 first downs and 6 points on Thanksgiving.

Alex Smith was taken a sack on 9.9% of his drop backs this year, after a sack 9.0% of the time last year. Colin Kaepernick is not Dan Marino or Peyton Manning; he is still taking a sack on 6.8% of passes, a number just below the league average but a big improvement over Smith. Of course, rush attempts are often sacks avoided, and the same is true of Kaepernick. Some of his rushes come on designed or option keepers, but a fair number of his yards have come from scrambles. Once we account for that in Kaepernick’s case, he is above average at avoiding sacks and making plays with either his arm or his legs.

Now, to Baltimore and Joe Flacco. Thirty-five quarterbacks, including Flacco, threw at least 800 passes in their first three years in the league, and had a below average sack rate. We see with the research on sack rate that it tends to belong to quarterback, and also tends to be a trait that carries forward. There are, of course, exceptions where quarterbacks can improve. Joe Flacco is one of only four quarterbacks to take sacks at an above average rate during the first three years, then be better than league average in both years four and five.

Flacco joins pretty good company in being an exception that has improved his sack rate. The other four are Troy Aikman, Warren Moon, Jake Plummer, and Jeff George. Aikman saw the Cowboys line improve and also became better at getting rid of the ball; he was above average for the rest of his career. Moon also became adept at getting the ball out of his hands and the shift held for the rest of his career. Plummer had a ridiculous number of sacks as a rookie, relying on his legs to escape trouble. By year three, he had turned it around, and the improvement in avoiding sacks remained. Jeff George is the only one of the group that regressed back after showing some improvement in years four and five. He also had the worst sack rate of that group in the first three years.

I have been critical of Joe Flacco in the past because of his propensity to hold the ball too long and take sacks. It was the one issue that I felt was holding him back from being mentioned in a higher class of quarterbacks. In 2011, he improved in that area, even as other measures declined. However, it looked like that was an anomaly, and he regressed in his sacks this year. Through 13 starts, Joe Flacco was taking sacks on 8% of his drop backs, a rate slightly worse than his first three years.

Then Cam Cameron was fired, and Jim Caldwell was promoted.

Lost among the impact of that change is how much Flacco has improved at avoiding sacks, as the Ravens are running the ball at a higher frequency, and he is getting rid of the ball. His completion percentage is actually down (a problem with focusing solely on completion percentage or over-counting it in passer rating), but it has come by throwing downfield, averaging 8.2 YPA, throwing 12 touchdowns to 1 interception, and taking a sack on only 4% of his drops.

He’s basically gone from regressing toward a younger Joe Flacco to becoming Drew Brees when it comes to getting the ball out. While you will hear the quarterback legacies debated and the eliteness garbage, Joe Flacco has already begun to emerge. We will see whether the move to fire Cameron carries over, but Flacco has changed his stripes.

It is the best of times in New Orleans for the 49ers and Ravens, and a hidden reason is what sack data tells us, and how each team has improved by different means.

[photo via USA Today Sports Images]