Roddy White, the franchise's all-time leading receiver, believes Armstrong has earned this head-coaching opportunity.
"He has worked hard and has managed a 53-man roster on a day-to-day basis, he knows the pulse of every team, and he has a lot of experience at the NFL level," White said. "He's an awesome guy and competitive as hell. He deserves to be a head coach for someone's team."
Armstrong, 54, has a second interview with the Cardinals on Friday. ESPN's Josh Weinfuss reported Armstrong is among a group of candidates that includes Philadelphia Eagles defensive coordinator Jim Schwartz and quarterbacks coach John DeFilippo, Patriots linebackers coach Brian Flores, Cardinals defensive coordinator James Bettcher, and Carolina Panthers defensive coordinator Steve Wilks. Pittsburgh Steelers offensive line coach Mike Munchak pulled out of a second interview with the Cardinals.
Arizona is looking to replace Bruce Arians, who retired after the season. Armstrong played running back, tight end, linebacker, and defensive back for Arians at Temple University was a graduate assistant coach for Arians in 1987 and has gotten a strong recommendation from Arians in the past.
"He's a leader of men," Arians said of Armstrong last August. "He's got grit, toughness. He's a great family guy. ... People get all hung up in these offensive and defensive coordinators, and special teams coordinators work with the entire team. So they have that presence and that connection with the offense, defense, everybody. To me, it makes more sense. Plus, he's had a background in both offense and defense."
Armstrong has been the Falcons' special teams coordinator since 2008. He interviewed for the Falcons' head-coaching position before Dan Quinn was named head coach in 2015. Armstrong has been through head-coaching interviews in Chicago, Kansas City, and Philadelphia through the years.
It's unclear which coaches Armstrong have in mind for offensive coordinator and defensive coordinator, but he's well-respected around the league and has plenty of connection from his two stints with the Falcons and years as the special teams coordinator with the Chicago Bears and Miami Dolphins. His current players believe he has the tools for immediate head-coaching success.
"Keith is a great motivator and communicator," long-snapper Josh Harris said recently. "As a special teams coordinator, you're tasked with coaching players from both sides of the ball. At some point, every guy on the roster is in a special teams meeting. His ability to relate to every player both on and off the field, combined with his wealth of knowledge, is what set him apart.
"He's always going to shoot you straight, and he's always got your back. Keith has played a pivotal role in my development, and the same goes for every player that's sat in one of his meetings. He is passionate."
If the Falcons lose Armstrong, assistant special teams coach Eric Sutulovich seems likely to be a top candidate to replace him.