LAS VEGAS -- The Atlanta Falcons hired Ryan Nielsen as defensive coordinator Friday, taking him from their biggest rival after he spent last season as the co-defensive coordinator of the New Orleans Saints.

The 43-year-old Nielsen spent the past six seasons with the Saints, where he was the defensive line coach all six years while adding the assistant head coach title in 2021 and co-defensive coordinator last season.

Since 2017, the Saints have recorded 281 sacks -- second-most in the NFL over that span -- and have finished in the top four in run defense in four of the past five seasons.

The Falcons on Friday also let go of three defensive coaches -- line coach Gary Emanuel, outside linebackers coach Ted Monachino and secondary coach Jon Hoke.

Nielsen is not in Las Vegas with the Falcons staff presently, as Atlanta is coaching in the East-West Shrine Bowl. Linebackers coach Frank Bush is the defensive coordinator for Atlanta at the East-West game.

The Falcons needed a new defensive coordinator after Dean Pees, the oldest coordinator in the NFL last season at age 73, decided to retire for the third time in his career to spend more time with his family, among other things.

Pees built a foundation for Atlanta's defense, both in the style they want to run and the culture they needed to permeate throughout the roster.

"It was a different system from what they had," Pees said. "So you had to get them to buy in."

The Falcons also had a young defense and turned over all but two starters from the 2020 team -- defensive tackle Grady Jarrett and cornerback A.J. Terrell -- by the middle of last season. While Atlanta finished No. 23 in points allowed and No. 27 in yards allowed in 2022, there was progress toward the end of the year.

The Falcons allowed more than 19 points once in their last six games and over 350 yards in one game over the second half of the season (351 against Pittsburgh) after allowing over 350 yards in six of Atlanta's first eight games.

After the season, Falcons head coach Arthur Smith said the franchise wanted to speak with a multitude of potential candidates before making a decision, but also wanted to focus on flexibility with whomever he brought in.

"When you are building that hybrid model, you're not looking for an overhaul," Smith said. "We've been building something here."

He didn't limit his search, having interviewed candidates with prior defensive coordinator experience, prior head coaching experience and those who have not been a full-time solo defensive coordinators.

When Smith hired Pees, he wanted an experienced playcaller who also could serve as a mentor for a first-time head coach to lean on. In Pees, Smith had that.

Where they are now, Smith said, is different than two seasons ago. By the end of 2022, the Falcons had only five defensive players left on the roster from the previous regime -- Jarrett, Terrell, linebacker Mykal Walker, cornerback Isaiah Oliver and safety Jaylinn Hawkins. Oliver is a free agent this offseason and both Walker and Hawkins are in the final years of their contracts.

Smith compared what he was hoping Atlanta could do to the Baltimore Ravens, who have had multiple defensive coordinators over the years and have made alterations to their scheme, but not to the type of players they looked for or the vision they had for the overarching plan of the defense.

"The way we've built," Smith said. "That won't change."

While with the Saints, Nielsen helped oversee the emergence of stalwart defensive end Cameron Jordan, who was named a first-team All-Pro in 2017 and second team in 2018 and 2019.

Jordan, for his part, took to Twitter to wish Nielsen farewell and to laud his strength in "developing (a) pass rush and emphasizing technique on run and gap integrity."

Nielsen grew up in Southern California and then went to college at USC as a defensive tackle and then became a volunteer assistant coach.

He spent the first 15 years of his coaching career in college, working with the defensive line at every stop along with being a defensive coordinator at Central Connecticut State in 2008 and 2009 and the co-defensive coordinator at Northern Illinois in 2012.