The Philadelphia Eagles are the first No. 1 seed to be an underdog in the divisional round since 1970. (Mitchell Leff/Getty Images)

The Philadelphia Eagles, the No. 1 seed in the NFC, are about to make history. And not the good kind. Their opponent Saturday, the Atlanta Falcons, is a 2.5-point favorite over the Eagles, according to the Westgate Las Vegas SuperBook, making Philadelphia the first No. 1 seed to be an underdog in the divisional round since 1970.

Only five previous home teams have been underdogs in the divisional round since the merger, but all were No. 2 seeds. Just one, the 2011 San Francisco 49ers, occurred in the 21st century. But there is a silver lining, Philadelphia: Those five were 4-1 despite being discounted by the oddsmakers.

Divisional underdog at home Spread Result
2011 San Francisco 49ers +3.5 Beat Saints, 36-32
1996 Carolina Panthers +3.5 Beat Cowboys, 26-17
1982 Miami Dolphins +1.5 Beat Chargers, 34-13
1981 Miami Dolphins +2.5 Lost to Chargers, 41-38, in OT
1979 Tampa Bay Buccaneers +4.5 Beat Eagles, 24-17

If the Eagles are going to increase that win total by one, they will need to see improved play from quarterback Nick Foles, who has been filling in for Carson Wentz, an MVP candidate before his injury, since Week 14.

Foles struggled in his three starts, completing 54.0 percent of his passes while producing a 77.7 passer rating. Perhaps even more important is how the Eagles offense has stalled with him under center. During the first 14 weeks, Philadelphia was scoring 2.4 points per drive, with a red-zone efficiency of 67 percent. Since then, it has scored just 1.2 points per drive with a 56 percent red-zone efficiency. The Eagles’ rate of drives going three-and-out has risen from 29 percent to 45 percent over that span.

2017 Eagles Points per drive Red-zone efficiency Three-and-out percentage
Weeks 1 to 14 (Carson Wentz) 2.4 67% 29%
Weeks 15 to 17 (Nick Foles) 1.2 56% 45%
NFL average in 2017 1.8 53% 35%

Offense like that won’t win many games. The 0-16 Cleveland Browns scored 1.2 points per drive during the 2017 regular season and, since 2002, the year the league expanded to 32 teams, teams won one of every six games (16.7 percent) in which they scored 1.2 points or less per drive. Foles and the rest of the offense have to improve quickly to have a fighting chance to win this game.

If not, Philadelphia’s defense needs to pick up the slack. Luckily, it appears to be up to the task.

Philadelphia was the fifth-best defense per Football Outsiders’ Defense-adjusted Value Over Average, which measures a team’s efficiency by comparing success on every play to a league average based on situation and opponent. The game charters at Pro Football Focus ranked the defense No. 2 overall, behind the Jacksonville Jaguars, for regular season performance.

Its biggest strength is a fearsome pass rush. Fletcher Cox, Brandon Graham, Chris Long and Vinny Curry earned high marks from Pro Football Focus; Graham, the seventh-best edge rusher per PFF, is dealing with an ankle injury, and it is unknown whether he will play Saturday. Still, Curry was ranked 18th among 57 qualified pass rushers by PFF, and Cox ranked seventh among 72 qualified interior linemen. Linebacker Mychal Kendricks was the sixth-highest graded linebacker, making 33 stops at or behind the line of scrimmage.

If the Eagles can get to Atlanta quarterback Matt Ryan consistently, their role as an underdog will look like a big mistake. Ryan’s completion rate falls from 71 to 51 percent under pressure. His passer rating drops from 100.1 to 72.7, roughly the difference between Wentz, a Pro Bowl passer, and Trevor Siemian, a questionable backup.

Matt Ryan in 2017 Completion rate Yards per attempt Passer rating
No pressure 70.9% 8.4 100.1
Under pressure 50.9% 6.2 72.7

Plus, Philadelphia boasts a significantly better run defense than Los Angeles did, and that, too, can be a major advantage.

Atlanta practiced a ball-control offense against the Rams on Saturday, rushing the ball 39 times. The vast majority of those, 33, were with the score within seven points, a departure for the Falcons from their regular season tendencies. Leading up to the first-round game, they called for a rushing play just 44 percent of the time with the game within a touchdown; against Los Angeles, that went as high as 52 percent. They only went higher than a 50/50 split four other times during the regular season — all wins — but shouldn’t do it again against the Eagles.

According to DVOA, the Rams had the 22nd-best run defense in 2017; the Eagles were ranked No. 3 behind the Arizona Cardinals and Denver Broncos. Philadelphia stuffed 28 percent of rushers at or behind the line of scrimmage during the regular season, 10 percentage points better than the Rams (18 percent). Plus, the Rams allowed 1.14 yards per carry by opposing running backs between 5 and 10 yards past the line of scrimmage, 28th in the league. The Eagles have allowed a league-low 0.88 second-level yards per carry.

2017 regular season Yards allowed per carry Second-level yards per carry Stuff rate
Eagles defense 3.8 1.14 28%
Rams defense 4.7 0.88 18%

Being able to limit both the run and the pass let the Eagles allow just 1.5 points per drive, the third-lowest mark of 2017. Over the past 15 postseasons, nine of the eventual Super Bowl winners ranked in the top five for points allowed per drive. The past two winners, the New England Patriots and Denver Broncos, ranked No. 1 and No. 2 during the regular season, proving defenses can, and do, win championships.

They can even make up for underwhelming quarterbacks.

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