ATLANTA — Frustration flowed through the Atlanta Falcons’ locker room, the players confused about how they had reached their lowest point and wondering how to climb out of it.

Late in the afternoon of Dec. 4, they had lost at home to the Kansas City Chiefs by one point, on a 2-point conversion return score in the final minutes. Their record dropped to 7-5 and suddenly they had grown vulnerable in the NFC South.

The season before, they had started 5-0 and tumbled out of playoff contention. The Falcons knew this team was better, much better, but they had also just invited another collapse. Defensive end Dwight Freeney, an 11-year veteran and Super Bowl champion, addressed his teammates in the moments after the loss.

“It doesn’t matter what we do from this moment,” Freeney told teammates, “other than try to get better.”

Since the loss to Kansas City, the Falcons have morphed into a monster. They have won all six games since, including two playoff games, by an average score of 39-19.

They went from a team competing for a playoff spot to a force that charged into the Super Bowl by dispatching the Seattle Seahawks and Green Bay Packers by a combined score of 80-41.

Their largest improvement happened on defense. Atlanta has held every opponent to 21 points or less except the Saints in Week 17, when they led 38-13 after three quarters. Players and coaches pointed to an overall change in their mentality, subtle but essential.

“I thought a shift took place for us,” Coach Dan Quinn said. “We knew we could play better. And that first shift took place. The unconditional support for one another, our intensity, took it up a notch. Then I thought another shift took place our first playoff bye week. We didn’t just kind of hang around. We had real intent on getting better and finding an edge.”

Even after they sunk to 7-5, the Falcons believed they had a team good enough to challenge for a Super Bowl, and not only because of their pyrotechnic offense. Falcons officials thought their defense had yet to unveil its potential, based largely on how it had been built.

General Manager Thomas Dimitroff and assistant Scott Pioli both came to Atlanta after running the New England Patriots’ front office. Working with Bill Belichick, they learned and developed a crucial tenet for assembling an NFL team: Talent needs to align with how the head coach wants to play. The driving philosophy for acquiring personnel should derive from the coach’s answer to a simple question: “What do you need?”

For Quinn, a former defensive coordinator for Pete Carroll’s Seattle Seahawks, that meant prioritizing speed on defense, which may be the most startling aspect of watching Atlanta play. Quinn’s schemes are predicated on defenders fast enough to play multiple, disruptive roles. One NFL personnel man said only the Seahawks have more defensive speed than the Falcons.

Most of it comes from players taken since Quinn took over two seasons ago. Second-round rookie linebacker Deion Jones, a hybrid player capable of handling the responsibilities of a safety or rushing quarterbacks from the outside, ran a 4.38-second 40-yard dash in his pro day. Second-year cornerback Jalen Collins had the fastest three-cone drill time of his class at the combine. Second-year defensive end Vic Beasley ran the 40 in 4.53 seconds, a time typically associated with a running back. At last year’s combine, rookie safety Keanu Allen had the longest broad jump of the class, a sign of explosiveness.

“They do a great job of drafting guys to play the scheme that they really want,” Freeney said. “That’s how Dan Quinn does it. We have some fast linebackers running side-to-side, safeties running side-to-side. They draft the right kind of people.”

As the season wore on, those young, fast defensive players Dimitroff had drafted started to better understand Atlanta’s defense and how to play with each other.

“The more you play together and gain experience together, the faster you can play,” Quinn said. “So we’re playing faster now than we did earlier in the season. Our speed hasn’t changed – we didn’t go lower our 40 times. But because of our communication, because of the style and attitude that we’re able to play with, we’re able to play faster.”

So even after they lost to the Chiefs in Week 13, the Falcons believed they were sitting on a dangerous team. To show it, players had to respond. Wide receiver Mohamed Sanu saw a rededication during the week. Teammates would remind each other, he said, “Just have the best practices you can.”

“We just made up our minds,” Sanu said. “We knew that what we had at the time wasn’t really us. We made up our mind and locked in.”

The next week, the Falcons crushed the Rams in Los Angeles, scoring two touchdowns on defense. They clobbered the 49ers the next week. “Something clicked,” Freeney said, “and we started playing great defensively.”

“There is something that kind of kicks in and I feel like it has for our team,” quarterback Matt Ryan said. “I really think it’s changed in our preparation. For the last two months, we’ve attacked the week the right way.”

At the start of December, the Falcons faced a shaky history and a crushing loss that reminded them of it. Few would have expected the Falcons to be preparing for a Super Bowl trip now. They shoved aside what didn’t matter and nearly two months later, have emerged as the best team in the NFC.

“It’s all about getting hot at the right time,” Freeney said. “People don’t realize that, all the stuff that happens in the regular season, all that is to try to get you to this type of position. We just focused on getting better. Defensively, we just stayed in the process. Now we look up, and look where we are.”