Simply put, Scoreability is the amount of yards gained by an offense, divided by the amount of points scored by the team. The number you get is how many yards a team averages per point. Multiply *that* number by seven, and that's the average amount of yards a team needs to gain to score a touchdown.
Sound complicated? It isn't.
A couple examples: the most efficient team in 2013 were the AFC Champion Denver Broncos, with a rating of 12.07 (606 points on 7317 yards). They score a touchdown every 84.5 yards gained.
Contrast that with the worst team in said category, the Houston Texans (who doubled as the worst team in the league, period). Houston rated out at 20.13 (276 points on 5556 yards). They would need 140.9 yards to score a touchdown in 2013.
Make sense now?
Ideally, to improve your standing in Scoreability, you need touchdowns, and lots of them. Settling for field goals, failing on fourth downs deep in opponent territory, and turnovers are all detriments to a Scoreability rating, naturally. Conversely, a team's defense and special teams units scoring touchdowns boost the Scoreability rating, as it's a metric that rates 'scoring efficiency'.
At first glance of the 2013 Scoreability chart, the Eagles provide a surprise: Philadelphia ranks merely 16th in Scoreability, checking in with a 15.10 rating (442 points, 6676 yards). That number sandwiches the Eagles between 15th-ranked Tennessee (14.89) and 17th-place Green Bay (15.36).
In other words, year one of Chip Kelly's up-tempo offense averaged a touchdown every 105.7 yards gained, though the number factors in two defensive scores (Najee Goode's special teams fumble return, Brandon Boykin's pick-six).
In Vick's six starts (even giving him full credit for Nick Foles' victory over the Giants when Vick left with a strained thigh), the Eagles scored 138 points on 2563 yards gained. That's a Scoreability rating of 18.57, or a touchdown every 130 yards gained. Such an awful number rates ahead of only Jacksonville (19.03), and Houston's aforementioned 20.13.
A Vick-led Eagles, had his numbers held all season, would have been the third-least efficient offense in the NFL.
How much did Foles improve the offense?
In his ten starts, Foles produced a Scoreability rating of 13.53 (304 points, 4113) yards. That checks out to a touchdown every 94.7 yards gained, a full 35 yards better than Vick's average.
The Eagles 13.53 Scoreability rating behind Foles would rank as sixth best in the entire NFL, behind Denver, Dallas (their defense killed them), Kansas City, San Francisco, and Seattle, in that order.
It's night and day.
It's no fluke that the Eagles went 8-2 in the regular season under Foles, while languishing at 2-4 under Vick. Even then, one of those wins can be credited to Foles and the defense pummeling the Giants in the fourth quarter.
Foles' efficiency was a breath of fresh air in 2013, and the numbers back it up.
Check out Cold Hard Football Facts and subscribe for the most comprehensive, in-depth statistics you need to know the game.
Follow Justin Henry on Twitter