Denver Broncos quarterback Bo Nix wasn’t very aggressive in the downfield passing game during Sunday’s 24-14 loss to the San Francisco 49ers.

Nix completed only two passes that traveled more than 10 yards down the field. He attempted just one pass of 20 or more yards against San Francisco.

According to Broncos head coach Sean Payton, the reason for Nix’s conservative approach wasn’t that he was afraid to push the ball down the field — it was because of the way the 49ers chose to defend Denver’s offense. 

San Francisco was willing to give up underneath yardage all afternoon. The 49ers played their safeties deep to take away the big plays, and they essentially dared Denver to work its way down the field a few yards at a time.

Broncos coach Sean Payton told reporters Monday that Denver noticed the 49ers’ approach while watching film. So the game plan was to take what San Francisco gave them underneath.

“We had seen this on tape,” said Payton of the 49ers’ defensive approach. “They did a pretty good job of staying on top of some of the deeper throws, and that’s part of what they’re trying to do defensively. Coming away from that game tape, I think the feeling overall was there was just more yardage underneath in different ways that I think we feel like we could have taken a little bit more advantage of.”

This approach isn’t unique to the 49ers. A lot of defensive coordinators across college football and the NFL are playing this way.

Teams don’t want to give up the big splash plays. They would rather make an offense earn it by driving the length of the field and picking up yardage in small chunks.

Part of the logic is that it gives more chances for the defense to force a takeaway.

And also, defenses are often perfectly fine with giving up a field goal in those situations. The thinking is that once the field shrinks in the red zone, it becomes much harder for the offense to finish drives with touchdowns (there’s less space to work with and fewer places to throw the ball).

It’s a patient approach. It also puts a lot of pressure on an offense to be efficient on every single snap.

But for whatever reason, Denver just couldn’t get the running game going against San Francisco. And without a productive ground game, the Broncos weren’t able to capitalize on the underneath opportunities the 49ers were handing them.

That’s the big concern with Denver’s offense right now. When a defense keeps its safeties deep, it’s practically inviting you to run the football. Lighter boxes should mean easier yards on the ground.

Denver didn’t get those yards. That made the short passing game carry more of the load than it should have.

If the Broncos see this kind of defense again (and they will, given how many teams are playing this way), the running game is going to have to be better. That’s the key to opening things up for Nix down the field.