49ers' Kyle Shanahan must make this one adjustment to beat the Eagles

This game will come down to Shanahan.

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Kyle Shanahan likes to call plays a certain way.

He has a run-first offense. He operates mostly out of 21 personnel (2 running backs, 1 tight end, 2 wide receivers). He wants the opponent to be in its base defense and to load the box to stop his run game. Then, he wants to call play-action passes over the middle that lead to big plays. He's a master at creating big plays against defenses that aren't great.

Last week, Shanahan faced a great defense and scored only three points. That's because the Seahawks were able to shut down his running game without loading the box or using their base defense. In fact, the Seahawks used their nickel defense the entire game and the 49ers still couldn't run the ball. As a result, the 49ers completed just one pass of more than 20 yards in the entire game and lost.

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This week, Shanahan and the 49ers will face another great defense -- the Philadelphia Eagles, whose defensive coordinator, Vic Fangio, has faced Shanahan four times and never given up more than 15 points.

Like the Seahawks, the Eagles will use their nickel defense practically the entire game. They will dare the 49ers to run the ball. The linebackers will not creep up to the line of scrimmage and give up the 15-yard catch over the middle.

Brock Purdy is one of the most efficient and prolific quarterbacks in the league when it comes to throwing over the middle. According to Josh Dubow of the Associated Press, Purdy is completing 72.6 percent of his passes on in-breaking routes, while the Eagles are giving up a minuscule 51.9 completion percentage on passes between the hash marks.

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Which means Kyle Shanahan can't call what he normally calls this Sunday. He can't be greedy. He can't hunt the big play because Fangio's defense won't give it to him. Fangio will force Shanahan to be patient and string together multiple long touchdown drives. And Fangio will force Purdy to throw the ball underneath and toward the sideline.

So, that's what Purdy has to do. He and Shanahan have to take what the elite Eagles defense gives them, and that will be a bunch of short passes. Take them. Check it down. Run the ball. Don't force it down the field, because you don't have the wide receivers to stretch the field. You lost that player when you voided the guarantees in Brandon Aiyuk's contract back in July. That was your decision.

Now, coach with the players you have, not the players you wish you had.