Smith said Tuesday tests revealed Tatupu will require season-ending surgery.
The Falcons report for training camp on Wednesday. Akeem Dent, a third-round pick from Georgia in 2011, and veteran Mike Peterson, who was re-signed on Monday, will compete for the starting job at middle linebacker when camp opens Thursday.
Curtis Lofton, the team's leading tackler the last three years, signed with New Orleans.
The 29-year-old Tatupu signed a two-year deal with the Falcons as a free agent. He did not play in 2011 following his release from the Seattle Seahawks before the season. Tatupu was a three-time Pro Bowl pick with Seattle.