It's unclear how long the Saints have known about Unger's plan to retire, but they did visit with at least one free-agent guard/center this week in Nick Easton.
Unger, who turns 33 next month, was officially placed on the NFL's reserve/retired list Saturday. He had one year remaining on his contract.
The Saints will save $6.95 million in cash and salary-cap space that he was due in 2019. They still will have to account for $1.75 million in "dead money" against the cap from his previous signing bonus.
Third-year center/guard Cameron Tom is among the likely candidates to compete for Unger's job. The Saints also have second-year guard/center Will Clapp on the roster. And they could turn to the free-agent market, though there aren't many top-ranked interior linemen still unsigned. Easton was a starting guard for the Minnesota Vikings in 2017, before he missed all of last season with a neck injury.
Unger quickly established himself as a captain and a leader for one of the best offensive lines in the NFL. The athletic 6-foot-5, 305-pounder missed only one game over the past four years for New Orleans, starting the other 67, including the playoffs. He made his first Pro Bowl as a member of the Saints this past season while they went 13-3 and earned the NFC's No. 1 seed before falling one game short of the Super Bowl.
Unger's previous two Pro Bowl nods came with the Seahawks, who drafted him in the second round out of Oregon in 2009.
Unger is now the second Saints veteran to retire this year, following tight end Benjamin Watson. The Saints also lost a second Pro Bowler this week after replacing longtime running back Mark Ingram with veteran Latavius Murray. Meanwhile, starting defensive end Alex Okafor signed with the Kansas City Chiefs, and the Saints also added defensive tackle Malcom Brown and defensive lineman Mario Edwards.