Dwight Harriman: I'm Dwight, known as Falconidae on the Atlanta Falcons message board. On that board, we have a crazed Ravens fan, who ever since Flacco won the Super Bowl has been incensed that Ryan was still rated ahead of Flacco. He's spent two years trying to convince Falcon fans that Flacco is a better QB. As you might expect, he has failed to win one convert.

So, can you explain to me why Andrew Luck is rated lower than Ryan last year. Also, why has Flacco has been rated lower than Ryan for their entire careers?

Any explanation you give will be appreciated. Considering that the Ravens fan is convinced that Ryan has gamed the system by throwing short passes, and that Flacco is penalized for his deep pass attempts, it probably won't do any good, but I would like to hear it.

Aaron Schatz: First of all, Dwight, you have to understand the historical irony of your e-mail. Once upon a time, in the Michael Vick days, we were basically seen as the eternal enemy on Atlanta Falcons message boards. Now we are the great defenders of Matt Ryan! How times change.

The first thing you need to understand is that Football Outsiders stats are not "grades," and therefore they shouldn't be considered as absolute judgments on whether Player A is better than Player B. We try to filter out a lot of context, but we can't filter out all context. We give stats, and then we use common sense to analyze what those stats mean given everything else we know about a player, including scouting reports. As I always say, that's why player comments in our book have words and not just tables of numbers.

To give three examples of places where the numbers are not perfect measurements of player worth:

We do not filter out the quality of a player's teammates, so what we're measuring is more "Matt Ryan and the Atlanta passing game" rather than just Ryan. That's important especially when considering Andrew Luck, who plays with some iffy receivers and a terrible offensive line. (The drop in Ryan's stats from 2012 to 2013? That's not Ryan. That's Julio Jones.)

There is something to be said for the idea that our stats could be improved by looking not just at what a quarterback does compared to average, but what he's done compared to average based on what the team asks him to do. Yes, it's harder to hit the deep throws that Flacco attempts more often than Ryan does.

DVOA is based on play-by-play so it doesn't account for things we analyze through game charting, like "dropped interceptions."

The basics of FO stats are explained on the site and while I don't give out the baselines that represent "average" in DVOA, I think the basic idea is understandable. I know people complain that it is a black box, but at least I tell you what's in the black box. (In other words, I'm telling you there is a ham sandwich in the black box. I'm just not telling you how many slices of ham are on it, or how much mustard. That's my secret recipe.)

As far as Ryan vs. Luck in 2013, guess what the number one issue is? SCHEDULE! Simple as that. The Falcons played one of the ten hardest offensive schedules in the history of Football Outsiders numbers, with their average opposing defense having -6.5% DVOA. The only teams that had it tougher: 2004 CIN/CLE, 2008 CIN/CLE, 1991 DAL, and 2004 NYJ. (Apparently, the Ravens and Steelers make life difficult on offenses, who knew?)

Luck played a tough schedule too, but not THAT tough.

So opponent adjustments boost Luck from 3.9% VOA to 4.6% DVOA but boost Ryan from 6.8% VOA to 13.3% DVOA.

After that, it looks like the issue is third-down conversions. Luck was average on third downs last year (33 percent conversion with 6.7 average yards to go), while Ryan was phenomenal (41 percent conversion with 7.3 average yards to go).

I also am guessing I don't have to explain why we have Ryan rated better than Flacco in 2013, right? Just career? Anyone with eyes could see that Flacco struggled last year. For their careers, again, this is not hard. Ryan has had a much higher completion rate over the course of his career. He's also had more yards per attempt, fewer sacks, a higher touchdown rate, and a lower interception rate.

In addition, 2013 wasn't the first time Ryan has faced a tough schedule. He's got a huge schedule adjustment for a tough schedule in 2008 and 2009 as well. He got a smaller adjustment downward for an easier schedule in 2011 and 2012, with his DVOA about 2.5% lower than VOA. 2010 is basically an average schedule. So that's three really tough years, two somewhat easy years, and an average year.

Flacco has gotten very little adjustment for schedule strength over the course of his career. He has only one season where a tough schedule boosts his DVOA by 3.5% (2008) and only one season where an easier schedule depresses his DVOA by around 2.0% (2009). Every other year, DVOA is roughly equal to VOA. By comparison, Ryan has three years where DVOA is over 5.0% higher than VOA.

Ryan has had better receivers than Flacco, but not by as much as you might think because Michael Turner was useless as a receiver and Ray Rice was awesome except for last season. In order to think that the difference in the receivers makes up the entire performance difference between the two, you really have to believe that Torrey Smith is the worst No. 1 receiver in the NFL right now.

Long answer, but a good debate to have a long answer to. Overall, I think it's pretty clear that Ryan has had the better NFL career, even accounting for Flacco's fabulous playoff run in 2012. But they were both very successful draft picks for their teams in 2008.