Bengals head coach Zac Taylor told reporters Green underwent his ankle procedure Tuesday morning, three days after the wideout was carted off the field during the team's first training camp practice.
"We're thankful that it wasn't a lot worse, and he'll get a chance to still show all the things that he was setting out to do this season," Taylor said. "He's a fighter. Although we feel bad for him, he's responded to adversity well in the past and this team will rally around him."
Green suffered a sprained left ankle and additional ligament damage, according to ESPN. Taylor declined to specify the ninth-year receiver's injury, but said it was more extensive than the Bengals thought.
Taylor said Green would miss multiple games when the season starts but didn't provide a specific timetable for the star pass-catcher's return.
"I don't like to make that projection because everybody heals a little bit differently, but we're ready for him to come back when he feels healthy and ready to go," Taylor said. "Hopefully, it's not more than a couple of games."
Green sat out seven games last season due to a right toe injury, the longest absence of his eight-year NFL career. He recorded 46 catches for 694 yards and six touchdowns in nine regular-season games last year.
The Georgia product is entering the final year of his current contract with the Bengals.