General manager Jim Nill said Friday that the expected recovery time is six to seven months.
Hanzal, who signed a three-year, $14.25 million contract on the first day of free agency in July, missed almost all of training camp and the preseason with an ankle injury. The 31-year-old Czech then missed 29 games with a variety of injuries, including to his back.
Nill said the back injury occurred in late November, and Hanzal had three injections to try to play through the pain. When Hanzal reached a point that he couldn't play, he opted for spinal fusion surgery.