Atlanta Falcons quarterback Tua Tagovailoa is out with what the club describes as a flare-up of an undisclosed injury, head coach Kevin Stefanski confirmed.

The team did not specify details on Wednesday, but reports indicated the issue involves a tight back for the veteran signal-caller.

With both Tagovailoa and Michael Penix Jr. unavailable, the Falcons moved to sign Cooper Rush to bolster their quarterback depth amid the sudden injuries.

Earlier in the day Atlanta cut veteran Trevor Siemian using a non-football injury designation, leaving undrafted rookie Jack Strand as the lone quarterback cleared to practice.

Tagovailoa will sit out Wednesday's session, though Stefanski expressed optimism he will return sooner rather than later, with sources noting the back problem is not viewed as serious and a return is expected next week.

Penix, Atlanta's Week 1 starter last season, continues to recover from right ACL surgery performed in November. He has taken part in spring individual and seven-on-seven drills but remains sidelined from full team work.

Stefanski said he is unsure when Penix will be cleared and will rely on medical staff for that timeline.

The club had counted on Siemian as the third-string option, yet now Strand, an undrafted free agent from Division II Minnesota State Moorhead, stands as the only healthy quarterback available on the first day of training camp.

Stefanski quipped that former star Matt Ryan, now the team's president of football operations, would not be taking any snaps despite the shortage.

"This is the NFL," Stefanski said. "You can't predict what's coming."

Rush, 32, played his first eight seasons with the Dallas Cowboys and appeared in four games last year with the Baltimore Ravens.