Spielman declined to speculate on whether Zimmer would have to miss multiple games during the recovery.

”We have to see how his eye responds to the surgery,” Spielman said. ”I do know how intense coach Zimmer is. Talking with him today and with the doctors, as much as he wants to be out there coaching tonight, it’s in his best interest that we get this taken care of. Coach Zimmer has never missed a game. I know how hard this is on him. I can’t express how hard on him it is that he won’t be able to coach. But we have to look after his health.”

Left untreated, retina damage can lead to permanent vision loss. This was the third procedure the 60-year-old Zimmer has had over the past month. He’ll stay at home to rest and not be able to attend the game, but Spielman said the coach would be allowed to watch on television.

”As hard-headed as he is and as tough-minded as he is, we had some pretty significant talks one-on-one, heart-to-heart, on what is important in life and what isn’t,” Spielman said. ”I think after we met, I expressed to him specifically that potentially going blind in one eye is not worth one game in the NFL.”

Zimmer, who got his start in the NFL as an assistant with the Cowboys in 1994 and spent 13 years with the organization, has yet to face Dallas in the regular season as a head coach . The Vikings and Cowboys played last year in the preseason.

Zimmer first experienced trouble with his right eye a couple of days before the Oct. 31 game at Chicago and scratched the eye inadvertently during that game. That prompted team doctors to send him for further examination, which revealed a torn retina. He had surgery Nov. 1 and another one Nov. 8, which left his eye noticeably red. It had cleared up significantly in recent weeks, though, and Spielman said at one point that Zimmer wasn’t expected to need further treatment.

But the coach suddenly complained of vision problems during a walk-through practice with the team Wednesday afternoon, and head athletic trainer Eric Sugarman drove Zimmer to seek medical attention. Spielman said the latest diagnosis was a detached retina.

After first revealing the issue at his Nov. 2 news conference, Zimmer said he’d been watching film with his good eye and using reading glasses to write down notes in preparation for that week’s game. With the Vikings mired in a slump with five losses in the last six games, the hard-nosed Zimmer sure hasn’t appeared to back off his approach in the desire to help the team get back on track and catch up in the NFC playoff chase. Zimmer mentioned recently he’s been arriving at his office even earlier than usual, around 4:15 a.m.

Spielman dismissed the theory that Zimmer’s setback this week was related to pushing too hard after the first two procedures.

Priefer, who’s in his sixth season supervising Minnesota’s special teams, has presided over some of the best units in the NFL. A former Navy helicopter pilot who has been a coach for 23 years and in the NFL for 15 seasons, Priefer interviewed with Chicago in 2013 for the head coach position that was filled then by Marc Trestman.

One year later, former Vikings punter Chris Kluwe posted a scathing essay on the sports gossip website Deadspin.com accusing Priefer of making anti-gay comments toward Kluwe while he was still on the team as a way of goading him for his gay rights advocacy. Priefer was eventually suspended for the first three games of the 2014 season and sent to workplace sensitivity training.

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