ORCHARD PARK, N.Y. — After six games of progress, the Broncos’ run defense relapsed on Sunday.

The Bills ran at will against Denver in the 20-3 thumping, gaining 244 yards on the ground.

Rookie Devin Singletary had his first 100-yard plus game while veteran tailback Frank Gore and quarterback Josh Allen rounded out Buffalo’s dominating ground game.

“They kept running it, and running it, and running it,” defensive end Derek Wolfe said. “We had a lot of missed tackles, and that was the story of the game. I missed two sacks, I missed a tackle for loss. Those were three huge plays you have to make in this league, and I’m just (completely) sick about it. I’m disgusted to come in here and get embarrassed like that.”

Singletary carried 21 times for 106 yards, while Gore added 65 yards on 15 carries and Allen had 56 yards, most of which came on improvised runs out of the pocket when the pass protection broke down. Gore moved into third on the NFL’s all-time rushing yardage list to toss some salt in the run defense’s wound.

“We’ve played good offensive teams and good backs before, but call it what you want, they did a better job of executing across the board today in the run,” safety Justin Simmons said. “It’s not on one group in the defensive unit. It’s on all 11 guys in the run game.”

Linebacker Todd Davis echoed Simmons’ sentiment and pointed out Denver’s inability to stop the run had adverse effects on the offense. Buffalo’s 244 rushing yards was the Broncos’ second-worst performance against the run this year, only better than the 269 yards by Jacksonville in Week 4.

So, despite limiting Buffalo to two field goals in the first half, the Broncos’ inability to stop the run resulted in over 10 more minutes of possession for the home team. Add in the fact that Denver came into the game ranked 11th in the NFL in rush defense, and Davis believes the defense deserves more blame for the loss than the offense, which had an atrocious day.

“I put this on us more than on the offense,” Davis said. “We’re supposed to play better, and we didn’t … We’ve proved we’re better against the run than this.”

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Josh Allen played according to the dual-threat scouting report. The quarterback was as willing to break off a nifty scramble to the sideline to move the sticks as he was to take on blows in the second and third levels of the open field.

“Allen made key plays on third down with his legs to keep the long drives going,” cornerback Chris Harris said.

Coach Vic Fangio credited Buffalo’s play-calling and acknowledged the Denver front showed schematic cracks.

“They blocked us good, their backs ran hard and I’m sure some of our (run) fits were off a little bit,” Fangio said.

So where does the Broncos’ defense go from here against the run, with a 3-8 record and the Chargers due at Mile High next Sunday? Back to basics, Wolfe said. If the Broncos touch a ballcarrier, they have to bring him to the turf.

“This isn’t the first time this year that we lost a game because we couldn’t tackle, because we couldn’t get the quarterback to the ground, because we couldn’t get the running back to stop falling forward,” Wolfe said. “We have to come together and keep pushing. We have five more weeks to be together as a unit, try to enjoy it and get what we can from it.”