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Defensive end Danielle Hunter underwent successful surgery on Tuesday and is expected to return to the field in 2021, according to coach Mike Zimmer.

Hunter underwent an operation to repair a herniated disc in his neck, a season-ending injury Zimmer twice called a tweak on Aug. 17 and Aug. 27, which was nearly two weeks after Hunter last practiced. Hunter initially thought the injury was due to a poor night's rest, according to Zimmer, as the team didn't have the full scope of the injury leading up to the season.

Zimmer said the team realized it was a more significant injury after an MRI "sometime during training camp." General manager Rick Spielman has previously said the team still didn't know the extent of Hunter's injury as late as Aug. 30, when they traded for defensive end Yannick Ngakoue.

"When you guys give me crap about this thing being a tweak, when it all started, he woke up and thought he slept on his neck wrong," Zimmer said Wednesday, "so that's why it was a tweak."

Hunter last participated in a non-padded practice on Aug. 14, after which a review of the practice film revealed a freak injury.

"It was.. hardly anything. Hardly anything," Zimmer said. "When we went back and looked at the tape from the previous, I don't know what it was, a week later, I mean, it could've happened to anybody at any point."

Before choosing to undergo surgery, Hunter got a second medical opinion in New York earlier this month. He's expected to make a full recovery, per Zimmer, who didn't provide a timeline for when Hunter can return to the field.

The two-time Pro Bowler is under contract through the 2023 season, and an NFL Network report last week suggested Hunter was unhappy with the deal that has him as the 18th-highest paid edge rusher by average annual salary.

Hunter is one of the NFL's best defenders when healthy, becoming the youngest player to 50 career sacks last year. He turns 26 years old on Thursday, and league sources have indicated to the Star Tribune that the Vikings would look to avoid a contractual standoff with Hunter in the event he seeks a new deal.