The most important QB stat no one talks about, but you should know it

In football, the three-man chain gang keeps track of down and distance on the sidelines.

The rod man holds the "rear rod" that marks the beginning of the current set of downs, the box man holds a pole that marks the line of scrimmage and has a box at the top indicating the current down, and the second rod man holds the "forward rod" indicating the distance required to gain a new series of downs. The two rods (also known as "sticks") are always exactly 10 yards apart, and the entire game of football is predicated on “moving the sticks” to achieve a new set of downs.

Teams that consistently move the sticks tend be the teams that win consistently. It follows that quarterbacks that move the sticks consistently are very good quarterbacks; quarterbacks that fail at this most basic of football tasks are usually not very good.

We measure QBs by all sorts of real and made-up stats, but there is no readily available stat that measures a QB's ability to move the sticks.

The simplest way to measure a QBs' ability to move the sticks is to add up his passing and rushing 1st downs and divide them by his number of dropbacks and runs. The resulting QB 1st-down percentage (or 1D%) may not be perfect, but it removes some of the inconsistencies that plague some other stats, i.e. it does not reward a QB for completing a 15-yard pass on 3rd-and-16, nor does it reward the QB for throwing a screen pass that the RB takes 80 yards for a TD. On the downside, because it's about first downs, it tends to undervalue QBs from big-play offenses, and tends to reward QBs who are able to sustain long methodical drives.

Let's take Dak Prescott's rookie season to illustrate the 1D% stat. Per Pro-Football-Reference.com, Prescott had 186 passing first downs on 483 dropbacks (458 pass attempts + 25 sacks), and 21 rushing first downs on 44 runs. In total, that's 207 first downs on 527 plays, a 39.3 QB 1st down percentage.

Last year, the 1st down percentage for all NFL QBs with at least 300 pass attempts was 34%, so Prescott's 39.3% looks pretty good. Just how good that percentage was becomes clearer when you see where Prescott ranks relative to his peers:

At the top of the table, you have Matt Ryan, Dak Prescott, and Drew Brees, and it's no coincidence that their teams are also the top three teams (1. ATL, 2. NO, 3. DAL) in Football Outsiders' Drive Success metric. These QBs (and their offenses) truly moved the sticks last year.

Most of the other QBs in the top ten are the names you expect to show up in any top ten list (Tom Brady, Aaron Rodgers, Ben Roethlisberger, perhaps Matthew Stafford). The surprise in the top 10 - at least for me - is Jameis Winston, whose passer rating of 86.2 would rank him 21st on this list. Which just goes to show that looking good as measured by passer rating and actually moving the sticks may not be the same thing. Winston may not throw the prettiest deep balls, and he may not always make the best decisions with the ball, but he's moving the sticks. Add the talent influx this year in Tampa, and the Bucs could go places; their quarterback certainly won't stop them.

In the list of 30 QBs above, 15 have a 1D% greater than 34%, 15 are below the league average. That means that the guys ranked from 11-15 (Alex Smith, Philip Rivers, Andy Dalton, Carson Palmer, and Marcus Mariota) were just slightly above average in moving the sticks last year.

From No. 16 on down you'll find guys like Sam Bradford, Derek Carr, or Russell Wilson, who got a lot of recognition for their play last year (all three had a passer rating in the 90s), but in terms of moving the ball, the numbers are clear: they were below league average.

And it gets progressively worse the further you go down the list, and you soon get into a situation where the quarterback becomes a key liability for the team, regardless of his draft pedigree, contract value, or “eliteness.”

At its core, football is about gaining at least 10 yards in three tries, and 1D% gives you a good idea of how successful a QB will be at achieving a new set of downs.

• A 1D% of 50% means that the QB and his offense is basically unstoppable, as every second QB play will achieve a first down on average. You could run once and throw twice and statistically you'd get a new set of downs every time until you stumble into the endzone.
• A 1D% of 33% means you'd get a first down after every third QB play. But that only works in a theoretical scenario where you don't have any run plays. In real life, teams will average at least one run in a three-play sequence, and if you only get a new set of downs on every third QB play, you're going to be punting a lot.
• A 1D% of 25% means you'd get a first down after every fourth QB play. That's terrible, and will mean a lot of three an outs.

We have just one game's worth of data for the new season, but I thought it might be interesting to see where QBs rank in 1D% after Week 1. Here's the data:

If you move the sticks effectively, you're bound to end up with a lot of scoring opportunities. The QBs at the top of this Week 1 list all had a great start to the season and their 1D% helped their team put up a lot of points: Derek Carr (26 points), Sam Bradford (29 points), Carson Wentz (30 points) and Alex Smith (42 points) top the table above and were involved in some of the highest-scoring games of opening weekend.

Others, like Eli Manning had a terrible outing on Sunday, and even Dak Prescott had a below average outing. Overall, as you look across the 2017 list (knowing that it's still way to early to draw any definitive conclusions), you gotta wonder if guys like Carson Wentz and Trevor Siemian will eventually fall back to where they ranked in 2016, whether guys like Dak Prescott or Tom Brady will find back to their 2016 form, and whether guys like Eli Manning or Joe Flacco will continue to get paid not to move the sticks as efficiently as their NFL peers.

For Cowboys fans, a breakdown of Dak Prescott's 1D% numbers for Week 1 could prove interesting. The following table lists Prescott's numbers by target:

What we can see here is that Terrance Williams and Cole Beasley were first down machines on Sunday night, Williams converting five of his seven targets into a first down, Beasley converting three of his five targets. That is pretty good.

Brice Butler had one long first-down reception on three targets, that's okay in the overall scheme of things. But there are two things that stand out here, at least from this game.

1. Jason Witten may be a reliable receiver, as seven of his nine targets resulted in passer rating-friendly completions, but only one of his receptions resulted in a first down, or more specifically, a TD. On Sunday night, Witten was a reliable target underneath, but he wasn't the first-down machine he's been in the past. And that's probably okay. A key part of moving the sticks is getting into manageable second and third down situations, and Witten certainly did that. Again, we can't draw any real conclusions from just one game, but perhaps that's his role on the team going forward.
2. The Dez Bryant/Dak Prescott connection did not work at all on Sunday. Nine targets, two receptions, one first down. That is simply not enough. If we remove Dez Bryant's numbers, Prescott's 1D% is at a cool 38.2%, which is very close to the 39.3% Prescott had last year. As bad as the failure to connect is, the good news is that if the Cowboys fix it, Prescott should be moving the sticks like he did last year.

Every few years I pick one particular stat that I watch closely over the course of a season. In 2010, that stat was adjusted passing yards (ANY/A), in 2014 it was the Aikman Efficiency Rating, and I feel like I've written about passer rating differential every year in between and since.

This year it's quarterback 1st down percentage, a stat no one talks about but you now know.