"I have worked with Mike in both Jacksonville and Atlanta and I consider him one of the best defensive minds in the game," said Koetter in statement. "I have worked alongside many coaches throughout my career, but Mike Smith stands as one of the best I've seen. He has great attention to detail, is an outstanding teacher on the field, and the right man to lead our defense. I could not be happier to have him on our staff."
Koetter and Smith were on the same coaching staff with the Jaguars in 2007. When Smith was the head coach with the Falcons, Koetter was Atlanta's offensive coordinator from 2012 through 2014.
Smith was the Falcons' head coach for seven seasons from 2008 through 2014. Smith posted a record of 66-46 with Atlanta.
Under Smith, Atlanta twice finished among the top five in the NFL in fewest points allowed.
Smith was out of football this past season.