Why the 49ers are struggling to run the ball with Christian McCaffrey

It's not what you think.

San Francisco 49ers running back Christian McCaffrey. | Stephen Lew-Imagn Images

SANTA CLARA -- Christian McCaffrey isn't having a bad season.

He's playing through a calf strain, and yet he's on pace for 1,065 receiving yards this season, which would be a career high. He's still one of the best receivers out of the backfield in the NFL.

As a runner, McCaffrey's success rate is 51.4, which is above his career average of 50.2. And he has broken five tackles in two games, according to Pro Football Focus.

And yet, McCaffrey is averaging just 3.5 yards per carry this season -- a career low. And his longest run of the season has gained just 13 yards. What in the world is going on?

Kyle Shanahan's take

San Francisco 49ers head coach Kyle Shanahan. | D. Ross Cameron-Imagn Images

To get to the bottom of this statistical oddity, I asked head coach Kyle Shanahan this week for his take on McCaffrey's rushing efficiency. Are opposing defenses simply stacking the box against him?

"No," Shanahan said. "It's actually more the opposite, more two-shell defenses and stuff. The blitzes were considered loading the box, but they're doing it with more two-shell stuff. But we haven't got a big one. I think it's harder to get big ones versus two shell. I think versus the Saints, we had the longest carry on them versus a two-shell defense in a year and one game. I think it was 13 yards.

"But, there are a couple plays that we've been one guy off on that I thought we could've got a big one on, especially versus some eight-man fronts. But it takes 11 guys to do it. You can't get a big one when one guy's off. But I'm not too concerned with the run game, but I'd like to get more production.”

So one guy has been off. Which guy has it been?

Christian McCaffrey's take

San Francisco 49ers running back Christian McCaffrey. | Stephen Lew-Imagn Images

After Shanahan discussed McCaffrey's production, McCaffrey talked about it at his locker.

"We're close," he said. "A lot of it is just I can't get tackled. That's on me. Being able to break these long ones comes from all 11 guys being on point and me stepping up and hitting those long ones."

It sounds like a blocking issue.

McCaffrey has been breaking tackles this season. Unfortunately for the 49ers, he has to break them in the backfield more than they'd like, particularly when he tries to run up the middle.

Through two games this season, McCaffrey has run the ball 13 times up the middle (through one of the two A-gaps, which are on either side of the center), and he has gained just 1.5 yards per carry on these plays. When he runs anywhere else, he's averaging 4.8 yards per carry, which is slightly better than his career average.

It seems like the 49ers' center-guard double teams aren't moving defensive tackles. And that's good to know. Now, they can call more runs off tackle.

Simple adjustment.