DENVER — The Denver Broncos had never allowed back-to-back 200-yard rushers.

Not only that, but in their storied franchise’s history—beginning some 68 years ago—they had never allowed multiple 200-yard rushers in a single season.

In fact, no team no team in NFL history had ever allowed back-to-back 200-yard rushers.

All of that changed on Sunday in their 23-20 loss at the hands of the Los Angeles Rams.

After the team’s second straight performance where they were embarrassingly unable to stop the run, Broncos’ head coach Vance Joseph pointed to one main reason why.

“As far as run defense, that’s a mindset deal. That’s not nice to look at,” Joseph said, not talking his way around it.

“Yeah that’s about right,” Von Miller agreed with his coach after the game that a mindset issue is plaguing the run defense. “We were going against a great running team, Todd Gurley, but still no excuses.”

Denver entered Week 5 as the league’s eighth-best rush defense, allowing less than 100 rushing yards per game to their opponents.

The New York Jets didn’t let that bother them as they pounded the ball on the ground 38 times for 323 yards, led by 219 yards from Isaiah Crowell on an NFL-record 14.6 yards per carry.

One week later, on Sunday, the Rams stole the Jets’ playbook and matched their execution, dropping 270 rushing yards on the Broncos’ once-great run defense on 39 carries.

Now, two weeks after ranking in the top 10, the Broncos own the league’s worst run defense.

The great Gurley was the beneficiary in Week 6, racking up 208 rushing yards and two touchdowns on a 7.4 yards-per-carry average.

What exactly is this “mindset deal” that Joseph blamed the run woes on?

“We didn’t tackle well, we didn’t fit well. It goes back to obviously having a mindset to stop the run. That’s two weeks in a row. Unacceptable,” he said, beginning his explanation to a major problem haunting his team.

“The tackling. The fitting. Getting off blocks. Early on, we tried to play more shell to keep the play-action pass from hurting us and we switched to playing more single high and loading the box and we couldn’t get [Gurley] slowed down. That’s a major issue when you’re trying to call defenses. If you can’t slow [the run game] down, it keeps the playcall off balance. It’s tough when you can’t stop the run.”

It’s also tough when it’s cold, in the words of Joseph, and on Sunday afternoon both were very true as the 25 degrees at kickoff made it the second-coldest regular season game in Broncos’ history.

Gurley had 88 first-half rushing yards, which is the third-most in his impressive career. But it was his 120 yards in the second-half that put the Broncos in a position where they had to recover an onside kick to have any shot of winning the game.

Despite holding red-hot Jared Goff to 50 percent completions, zero touchdowns, one interception and a 58.5 passer rating, Denver’s defense still allowed 444 yards of offense because of their inability to slow down the run game for a second-straight week.

“The ball coming to me, I just can’t. I just can’t get it done,” Von Miller said, looking for words on why the run defense has been historically bad the last two weeks.

“I’ve got to watch the film and figure out what I can do to make things happen. We knew we were going to be a little leaky in the run today because the pass was our focus, but 270 yards is just ridiculous. I got to do better.”

Under Rams head coach Sean McVay, Los Angeles has never lost a game in which Gurley complied at least 140 yards from scrimmage.

Gurley easily eclipsed that, racking up 225 yards, thanks in large part to the 208 yards on the ground. McVay continued his streak, too, sending Denver’s its fourth-straight loss.

The Broncos and Joseph now have a short week to straighten out their mindset as they face a talented David Johnson and the Arizona Cardinals on Thursday night.