We can figure out how many games a team "should" have won in a given season based off their point differential by calculating their Pythagorean expectation, a metric invented by Bill James for baseball and applied to football by Daryl Morey. More often than not, teams whose win total outstrips their Pythagorean expectation will decline the following year, as was the case with the 2016 Panthers and Broncos.
The opposite is true for teams who underperform their Pythagorean expectation, which helped push the Cowboys, Giants and Titans toward winning records last season.2017 impact: The Raiders won 12 games but outscored their opponents by only 31 points, producing a Pythagorean expectation of 8.7 wins.
Adjusted net yards per attempt (or ANY/A) uses more modern research by Chase Stuart to estimate the value of touchdowns and interceptions while also incorporating sacks, which evidence suggests has plenty to do with quarterbacks despite being commonly blamed on the offensive line.
Historically, with precious few exceptions, teams will win games that are decided by seven points or less about 50 percent of the time.
Even if teams with terrible records in one-score games might improve 90 percent of the time the following year, nothing is guaranteed in the NFL.
The simplest individual metric with which to judge quarterbacks is yards per attempt (YPA), which shouldn't require much explanation.
On the other hand, the Eagles finished fourth in DVOA -- between the Falcons and Steelers -- but won only seven games, thanks in part to a tough schedule.
DVOA would expect Houston's record to decline and Philadelphia's to improve next season.
DVOA was created by Aaron Schatz of Football Outsiders and serves as his site's core metric.