The San Francisco 49ers NFC Championship opponent this Sunday is the Philadelphia Eagles after the NFC West champs took out the Dallas Cowboys 19-12 last week. The story of that Divisional Round game was the No. 1 ranked 49ers defense, which held the high-powered Cowboys offense to just one touchdown and two field goals. On offense, it was seventh-round rookie Brock Purdy connecting with tight end George Kittle for 95 of his 214 yards. Last year’s “Mr. Irrelevant” has been one of the stories of the season, coming from obscurity and winning his first seven starts to get his Niners within a win of the Super Bowl. However, for the upcoming 49ers-Eagles tilt, the 49ers' X-factor isn’t the young quarterback, it’s the running back the team traded for midseason.

49ers X-Factor vs. Eagles: Christian McCaffrey

The 49ers are very much on the Los Angeles Rams' track of mortgaging the future to win in the present. The franchise traded first-round picks in 2022 and 2023 in order to trade up in 2021 to draft Trey Lance. That didn’t work out perfectly, but the way Brock Purdy stepped in, the damage has been negated.

What did work out well was the October deal for Christian McCaffrey. In that move, the 49ers send the Carolina Panthers a second, third, and fourth-round pick in 2023 as well as a fifth-rounder in 2024. In return, the Niners got one of the most versatile offensive weapons in the NFL.

Since going to Carolina with the No. 8 pick in the 2017 NFL Draft, McCaffrey has been one of the best offensive players in the league… when healthy.

In his best season, 2019, McCaffrey ran for 1,387 yards and has 116 catches for 1,005 yards. He led the league in total touches (403), total yards from scrimmage (2,392), and total touchdowns (19). That season, he made the Pro Bowl and All-Pro teams. Unfortunately for the RB and NFL fans, he only played 10 games the next two seasons.

This year, splitting time between the Panthers and 49ers, McCaffrey is back to his old form. He has 244 carries for 1,139 yards, 85 receptions for 741 yards, and 13 touchdowns. And most importantly, McCaffrey has stayed (mostly) healthy with the 49ers, which means in the 49ers-Eagles game this weekend, he should be ready to go full bore.

McCaffrey’s current team will need every bit of his talent and his efforts in the NFC Championship vs. the Eagles.

The Eagles boast the No. 1 passing defense in the NFL in 2022, giving up just 3,057 yards through the air this season. They’ve only given up over 100 yards to a pass-catcher once in the last seven games. That’s bad news for Purdy, Deebo Samul, Brandon Aiyuk, and George Kittle. Between the Eagles' pass-rush and excellent secondary, they could shut down the 49ers passing game, which has been a key to this point in the playoffs.

However, the Eagles D is more vulnerable against the run. Last week against the Giants, New York’s only score came on an eight-yard touchdown run by Matt Breida set up by a 39-yard scamper by Saquon Barkley.

McCaffrey and the running game will be important in the 49ers-Eagles contest, but the 49ers X-factor himself will be the key. Philadelphia led the NFL this season with 70 sacks, which is 15 more than the second-place Kansas City Chiefs. McCaffrey will be the relief valve out of the backfield when Purdy is under pressure. The screen game will help counteract some of the Eagles' pass rush, as will running at the Philly edge player, Brandon Graham, Josh Sweat, and Haason Reddick.

Long story short, everything that the 49ers are able to do on offense will center on Christian McCaffrey.

And if the 49ers' X-factor can start to dominate the game on Sunday, San Francisco will have a real chance to open up the offense.

If the Eagles’ cornerbacks start peaking in the backfield, and the safeties come up in the box to stop the run, and the linebackers bite on play action, and the linemen hesitate to guard against the screens and draws, that’s when Purdy can go over the top to Kittle, Samuel, or Aiyuk.

In the end, if the 49ers NFC Championship game ends in a Super Bowl berth, most people will talk about how Purdy went from “Mr. Irrelevant” to the most relevant player in the league. Everyone loves the quarterback.

But if the young signal-caller has success, it will almost certainly be because of his backfield mate, Christian McCaffrey. He is the 49ers' X-factor, and if the team wins, while he may not get the lion’s share of the credit in the media, he absolutley will in the San Francisco locker room after the game.