The ability to generate pressure on the opposing quarterback, while preventing it to your own, is arguably the principal element by which games are won. (I mean, after roster talent, coaching, and game planning...)
Every quarterback in the NFL plays worse under pressure.* Every defense in the NFL plays better when it can generate pressure. If the NFL is a passing league, pressure on the passer thus is of paramount importance.
*Pressure is not necessarily synonymous with blitz; rather this typically refers to standard four-man rush pressure.
Sacks are the most tangible element of pressure. QB hits and hurries are great, too, but harder to quantify. If you watched the AFC Wild Card game between the Ravens and Steelers, you saw that pass rush was the difference in the game. Baltimore sacked Big Ben five times, repeatedly killing their drives, stifling the league's second best offense. Pittsburgh came close a few times but only got Flacco once.** #5 carved them up as a result.
**That one sack did produce a terrifying fumble that Baltimore fortunately recovered.
Sack rate is an interesting underlying number because raw Sacks are a product of volume. For example, a team that generates 49 sacks on 600 opposing pass attempts (8.2%) technically was not better than the team with 45 on 500 attempts (9%). Counting stats like sacks are easier to grasp and probably matter more in the real games, but rate stats help provide a picture of real performance.
Sack rate is simply (Sacks / (Sacks + Pass Attempts)). Football Outsiders has an even more advanced version that accounts for down and distance and aborted snaps but a) I don't have a paid sub to that database and b) let's keep it simple so you aren't bored to death (which you might be already -- sorry).
Below are the team's best four and worst three offensive and defensive sack rates since 1996:
2013 was not a good year. The Ravens suffered their second highest number of offensive sacks in a season with 48, but they also had a franchise high 619 pass attempts. It was actually only their 7th worst season in sack rate but it felt worse because of how futile the offense's effort was that year.
2014 was light years better. It was nearly their best year ever in pass protection, narrowly edged only by the 2006 team. And it felt like half of those 19 sacks came against J.J. Watt and the Texans in Week 16.
2003 was a laughingstock, tied for worst in the NFL and nearly a franchise-worst. Given that the Ravens had their best rushing season ever in 2003, I think we can safely conclude the quarterback had a big role in that sack number. Thanks, Kyle Boller.
Baltimore's studly pass rush turned in one of its better years last year, almost exactly on par with 1999, when Peter Boulware had his best season (by AV) and made All-Pro.
As you can see in the table, the 2006 team was just ridiculous in both categories. I need not say more. Defensively, 2011 and 2003 were fantastic, too, coming in at 3rd and 1st in the NFL in their respective seasons.
It seems strange that 2010 was such a low producing team in sacks. They were the worst team in the NFL that year in sack rate although they were the third best in opposing quarterback Yards/Attempt. It is possible that they made up for fewer sacks with pressures and quarterback hits (which are almost as good) but strange nonetheless for a 12-4 team.
Role of the QB
Sacks are sometimes unfairly viewed as only the fault of the offensive line. Certainly the line has a big role but the QB has a very underrated role in them, too.
Look no further than the NFL all-time leaderboards in sack rate. You'll see some familiar names at the top who did not have great offensive lines. That is no accident. Those QBs have made average offensive linemen (like Jeff Saturday and Jermon Bushrod) look like Pro Bowlers/All Pros for years. Getting the ball out quickly while moving around in the pocket to evade initial pressure are key attributes.
As I mentioned, the 2003 Ravens team had its best rushing season but nearly its worst season in pass protection. In a word: Kyle Boller.
This year, Joe Flacco significantly improved his ability to evade sacks compared to his career average, aside from getting better protection. Two key reasons for that:
1) Improved run game. 3.1 YPC isn't going to keep anyone honest. 4.5 will.
2) Moving to a West Coast scheme under Kubiak, away from Cam Cameron's Air Coryell scheme. Fewer long-developing iso routes and more short and intermediate passing meant fewer sacks and better sustained offense, at least in 2014. Also, Kubiak was just a better OC than Cameron.
A note about the legendary 2006 team
The more I study Ravens' history and statistics, the more reverence in which I hold that 2006 team. Aside from its well known astonishing array of talent and production, it set franchise records in virtually every conceivable statistic available.
Sack rate was one. Steve McNair had the second best sack rate in the NFL in 2006, behind only Peyton Manning. The 2006 Ravens had the 50th best sack rate on offense in NFL history, a pretty respectable number. Less than 10 active QBs/offenses have done better and only one of those QBs (P. Manning) did it more than once.