NFL betting, odds: Does Brock Purdy's improbable run come to an end against Eagles?

The Philadelphia Eagles were the clear favorites to win the NFC through the first 15 weeks of the season. Then everything slowly started to shift. An injury forced Eagles QB Jalen Hurts out of action in Week 16, right around the same time it became clear the 49ers were a legitimate threat to the NFC crown with Brock Purdy under center. San Francisco's rookie quarterback continued to pass every test while building on a 49ers win streak that dates back to Week 8 of the regular season. So while the 49ers didn't overtake the Eagles on the odds board until the end of the year, it became clear much earlier that the NFC was a two-team race.

Whether you are discussing either team's offense or defense, it's the unstoppable force vs. the immovable object on many levels. The 49ers rank No.1 in pass DVOA under Purdy, and guess who has the No. 1 pass defense? The Philadelphia Eagles. There will also be a war in the trenches. The Eagles run the ball better than any team in the league, while the 49ers' defense ranks second in stopping the run. Both teams looked like the best in the conference at various points in the season, and now they collide at full strength. How do you handicap such a competitive game? You look for exploitable matchups, tendencies and the likely scenario for how the game will play out.

San Francisco 49ers quarterback Brock Purdy (13) looks to pass during an NFL divisional round playoff football game against the Dallas Cowboys, Sunday, Jan. 22, 2023, in Santa Clara, Calif. (AP Photo/Scot Tucker)
Brock Purdy and the 49ers have been a different team on the road this season. (AP Photo/Scot Tucker)

San Francisco 49ers at Philadelphia Eagles (-2.5)

The field is pretty even now that we are down to the final four teams, but these two are as close to the Spiderman meme as you will see. Two teams with explosive playmakers, strong rushing attacks and great pass rushes. The defenses win differently, and San Francisco's is stronger overall. But I will explain later why it is also the most vulnerable.

The game script will be a significant factor in determining who is going to Arizona and who is booking flights to Cancun. The Eagles have been the league's most potent scoring offense in first halves, particularly at home (19.1 ppg), and San Francisco's defense has allowed the second-fewest amount of points. There are a lot of factors pointing to the Eagles getting off to a fast start, starting with their ability to exploit the 49ers' biggest weakness on defense: allowing big plays in the passing game.

San Francisco's pass rush is typically disruptive enough to mask its challenges on the back end, but doing that against the Eagles seems highly improbable. Philadelphia is PFF's highest-graded pass-blocking unit. Also, the Eagles led the NFL in explosive plays (rushes of 10-plus yards, passes of 20-plus yards) with 137 and were second to only Kansas City through the air with 63. So if the 49ers can't get to Hurts early, Philadelphia is very likely to get out to a big lead. Deep passes down the field are kryptonite to this 49ers defense, and the Eagles have the playmakers to exploit it with A.J. Brown, DeVonta Smith and a healthy Hurts.

Outside of the Eagles' offense meshing perfectly with San Francisco's most significant vulnerability, there is also the Purdy factor. During the 49ers' impressive three-month winning streak, they have played only three road games and only two with Purdy, a 21-13 win over Seattle and 37-34 OT win at Las Vegas. So it makes sense that Kyle Shanahan, who has a long history of being tight in big games, will start with a very conservative offense to help his young quarterback ease into his first playoff game on the road. It's a gigantic leap from Las Vegas and Jarrett Stidham in Week 17 to playing in the NFC championship in a loud, hostile environment against a defense that recorded 19 more sacks than any other team in the league. As Purdy gets acclimated, it's likely Hurts is putting the ball in the end zone on the other side.

How Shanahan and the 49ers respond will go a long way in determining whether this one goes down to the wire. San Francisco certainly has the talent to punch back with the running game by re-establishing tempo and using the formula that helped Washington hand the Eagles their first loss. However, Philadelphia's run defense has improved since Jordan Davis returned from injury, allowing only a 32.3% success rate in non-garbage time situations over the last four games. The 49ers are only 4-3 on the road this season, with losses at Chicago, Denver and Atlanta. Despite winning two road games with Purdy, they looked like a much different team in both games.

Home-field advantage matters with an inexperienced QB on the other side. I'm betting the Eagles get out to an early lead and battling back from a big deficit on the road in this environment is too much for Purdy to overcome. Back the home favorite and lay the points. Philadelphia -2.5

Stats provided by PFF, teamrankings, rbsdm, Football Outsiders.