ARLINGTON, Texas – They were celebrating last week, having shown their resolve and mettle in New Orleans. A week later, the Atlanta Falcons barely showed up.

Nothing went right Sunday for Atlanta -- not on offense, not on defense, not on special teams. While some of that could be attributed to the topsy-turvy ride that is life in the NFL, the swings usually aren’t this bad, like they were in a 43-3 defeat to Dallas that was the team’s worst loss since 2004.

“We were outcoached,” coach Arthur Smith said. “And outplayed.”

It’s fair to wonder if any of this came as a result of a hangover from the team’s dramatic win over New Orleans, where quarterback Matt Ryan had yet another last-minute comeback to beat the Falcons' biggest rival. Both Smith and Ryan said they didn’t see anything during the week of practice that indicated what happened Sunday -- a complete failure in every way -- could be a possibility.

Variance happens with almost every team, including one like the Cowboys, considered one of the league’s best. Just look at Dallas -- lose by 14 to Denver a week ago, win by 40 this week. Atlanta is a team trying to shift its culture -- it hasn’t been over .500 since the end of the 2017 season -- so this type of up and down is surprising, but not shocking. Whether there was a hangover is reasonable to wonder but impossible to tangibly prove.

“You would certainly hope not. You could make that argument,” Smith said. “That falls on me. I didn’t get the team ready to go. You come off a big win and you’d like to think that doesn’t have an effect but I can’t speak to that. It didn’t change my preparation. I felt we had a pretty good week.

“But the way the game started, and really that second quarter, it’s hard to argue otherwise.”

Everything led to poor results for Atlanta. Ryan’s 117 yards were the fewest of his career when he attempted at least 10 passes. His nine completions tied for the third-lowest number of his career -- and his lowest number of completions since 2012. Of his 21 pass attempts, 10 were credited as passes defended by Dallas players.

His 42.9 completion percentage was his worst since Dec. 4, 2011, when he completed 42.55% of his passes in a loss to Houston. His 21.4 passer rating was the worst of his career.

Ryan said “it was early” when everything began to fall apart for Atlanta. But it continued throughout. The Falcons didn’t convert a third down until there was 6:15 left in the game -- after missing on their first nine. No Atlanta wide receiver gained a yard in the first half, and Olamide Zaccheaus was the only Falcons receiver to have more than one reception (Kyle Pitts, a tight end, had four catches for 60 yards). Russell Gage, the team’s top receiver, was held without a catch for the second time in three weeks.

It was way more than Ryan, though. It was an obliteration on every level, a game where Atlanta’s same old problems (not much of a run game and a woeful defense) found company with newer, perhaps more pressing issues (an ineffective Cordarrelle Patterson, special teams snafus and Ryan’s worst game as a pro).

The high point of holding Dallas to a three-and-out on their second possession was followed by touchdown, touchdown, touchdown for the Cowboys’ offense and punt, punt, blocked punt for Atlanta’s. None of Atlanta’s defensive backs could cover CeeDee Lamb in the first half and it showed after seven targets, six catches, 94 yards and two touchdowns.

By halftime, the only question was how big Dallas’ win would be.

“We didn’t play well anywhere,” Ryan said. “It’s not about any one position. Across the board, we all didn’t take care of our business and we can do better than that and we need to.”

The Falcons are hoping this is an aberration, a down point in what had been a fairly competitive season. The Falcons play at home Thursday (8:20 p.m., Fox) against a New England team that pummeled Cleveland, 45-7.

Smith and the Falcons will face a difficult turnaround. And how Atlanta responds against New England will show whether this team is more like the one that beat the Saints or the one that was blown out by Dallas.