Days after his defense faced a late comeback attempt for the fourth time this year, and withstood it for the second time, Mike Zimmer summed up the spurts of progress for his young secondary thusly:

“They’ve all made improvements, each one of them in different areas,” Zimmer said Wednesday, after the Vikings held off a late Packers comeback in a 28-22 win last Sunday. “I know [Jeff] Gladney had some bad plays this week, but he had some good plays as well. Those are the kinds of things you’re looking for, these good plays where they — really, what I’m looking for out of these guys is not so much ‘paint by the numbers.’ It’s a little bit more, ‘Oh, I can kind of anticipate what they might be doing here based off the split or the motion or the receiver that’s in there.’ Right now we’re still in kindergarten, but we’re trying to get to a master’s program here quickly.”

The Vikings are in a new phase with their defense, brought on by a wholesale exchange of experienced (and expensive) players for younger options and a pandemic that wiped out precious instructional time this summer.

Injuries have ravaged an already-inexperienced group, to the point where two rookies (Gladney and Cameron Dantzler) have already played more than any other first-year corner under Zimmer in Minnesota and two more (Josh Metellus and Harrison Hand) were on the field at the end of the game Sunday, trying to help preserve a Vikings lead against Aaron Rodgers.

A defense that has long been able to avoid big plays through sound understanding of the scheme and mastery of intricate details has instead absorbed an outsized share of haymakers.

In Zimmer’s first six years as head coach, the Vikings gave up only 257 passing plays of 20 yards or more, the second-fewest in the league during that time. They did not allow more than 47 in a single season. This year alone, they have allowed 30 in just seven games, fewer than only Atlanta and Cincinnati.

Whether by hubris, miscalculation, bad luck or some combination of the three, the Vikings defense has gone through a first half like none other in Zimmer’s tenure. But as he’s inherited a new group of pupils and an unorthodox set of challenges, the coach has seemed energized by the task, speaking of how he’s been invigorated by the chance to mold a new group and periodically turning news conference questions into teaching sessions on cornerback technique for his players, fans or anyone in between to hear.

Minutes after the Vikings had left Lambeau Field’s blustery winds for a climate-controlled locker room, Zimmer appeared on a Zoom call, alternately wiped out and fired up about what he’d just seen.

“Right now, I think I got to get some of that — what’s that Hair for Men stuff called to get the gray hairs back out?” Zimmer said. “It was very, very hectic on the sideline today.”

He noted a rookie running on the field when he wasn’t supposed to be there and earning a penalty, having so many injuries at corner that he didn’t have a nickel back, corners watching Rodgers instead of the receiver. But, he added, there were “many things hopefully we can teach off of this tape and be better for it in the future.”

As the Vikings get ready to close out the first half of the season at home against the Lions on Sunday — with one corner on injured reserve, three more out for the game and another questionable with a hamstring injury — here is a look at four facets of cornerback technique they’ve tried to improve: how they use their heads, their eyes, their feet and their hands.

Head

Zimmer has talked for years about the importance of situational awareness for his corners: that they understand how things like the score of a game, the time left on the clock, and the down and distance will change the route concepts an offense will use.

Zimmer wants corners paying attention to the receiver’s speed off the line of scrimmage and the angle of his release to determine what route he will run.

Just before halftime in the Vikings’ season-opening loss to the Packers, Dantzler found himself in a compromised position. He decided to press Marquez Valdes-Scantling with 21 seconds left in the first half, even though the Packers were at the Vikings 45 with one timeout and would likely be looking to go downfield. Rodgers hit Valdes-Scantling for a touchdown that gave Green Bay a 22-10 lead.

“There’s 25 seconds left in the half, and he’s trying to play bump-and-run on the receiver instead of understanding the situation there,” Zimmer said after the Vikings’ 43-34 loss.

When Dantzler gave up a 39-yard completion to D.K. Metcalf on a fourth-and-10 that helped the Seahawks drive for the game-winning score on Oct. 11, Zimmer actually saw a sign of improvement. Dantzler started the play 7 yards off Metcalf, knowing quarterback Russell Wilson would need to stretch the field. He lost track of the ball when it was thrown near the sideline and he tried to turn his hips, but Zimmer said the day after the game the rookie started the play in better position.

“Right before the half, Cam Dantzler against Green Bay: He’s in the wrong position and gives up a big play. This time, understanding the situation, he was actually in great shape on the play — just misjudged the ball,” Zimmer said Oct. 12. “Instead of going up and getting it, he’s waiting for it to come down. They’ve got a good receiver and he came down with it. I think the more times you put them in these situations, unfortunately, you learn these kind of things. …

“They’ve got a lot of things on their plate, learning who the good receivers are and where their splits are and how the receivers run their routes, studying where the back is. I mean, all the different things that they have to learn. And now we have to put it into the fourth quarter and these two-minute situations where they understand, ‘OK, now is not the time to be aggressive, now is the time to be cautious.’ It’s all a learning process for them.”

Eyes

The young Minnesota corners have been victimized when they’ve looked in the wrong spot, particularly in the red zone, where veteran quarterbacks like Wilson, Rodgers and Matt Ryan have exploited momentary lapses in coverage.

Zimmer quipped after the Packers game on Sunday that some of his young defenders “were just wanting to watch the Hall of Fame quarterback instead of watching their guy” in the first half. The coach threw his hands up in the air as Gladney returned to the sideline after giving up a 5-yard score to Davante Adams on the Packers’ first drive.

“ ‘17’ is a guy we’re obviously paying a whole bunch of attention to,” Zimmer said the day after the game. “He’s lined up on the outside shoulder of him. He’s got Anthony Harris on the inside. The ball is snapped, [Adams] gives him a little shake, [Gladney] looks inside and then he gets beat to the outside, where that’s where he should’ve been all the way. There’s a lot of little things like that I’m trying so hard to get these young kids to understand not only about their position but the guy they’re playing against, where their help is.”

The same thing happened on Adams’ second touchdown, when the receiver motioned inside before running a pivot route back to the outside while Gladney was peeking back at Rodgers.

“That’s probably what they’re having the hardest time with right now: They never transfer their eyes back to the receiver and get back into the position they should be in,” Zimmer said.

Feet

In college, when receivers aren’t as skilled and quarterbacks aren’t as precise, corners tend not to pay the price for being slightly out of position as often as they do in the NFL. The Vikings’ past three games — against Wilson and Metcalf, Ryan and Julio Jones/Calvin Ridley, and Rodgers and Adams — have put their corners in situations where they’re liable to give up big plays if they’re not lined up with proper leverage or they’re drifting out of position.

The Seahawks’ fourth-down game-winner from Wilson to Metcalf came when Dantzler passed off the receiver on a crossing route, staying in his position to play Freddie Swain crossing his way instead of following Metcalf in man coverage.

NBC’s cameras captured safety Harrison Smith after the play, telling Dantzler (in so many words) to cover his man.

The following week, Ryan hit Jones for a TD on third-and-11 when Dantzler lined up too far inside of the receiver, giving Jones room to break outside even though Dantzler had help from Smith to the inside.

“It’s been a lot of learning by fire,” Zimmer said on Oct. 18. “The first touchdown when it was third-and-11, Dantzler had help on the inside and he got in a bad position.”

Later in the game, on a 31-yard pass to Jones, Dantzler “was in good position, but didn’t close to the receiver,” Zimmer said, “and the ball was a little underthrown, but he didn’t find the ball.”

Hands

Zimmer has urged his young corners to challenge receivers more effectively, but the Vikings haven’t had as much trouble with Dantzler or Gladney grabbing receivers like Xavier Rhodes or Trae Waynes did early in their careers. Gladney, Mike Hughes and Holton Hill were flagged for illegal contact in the Week 2 loss to the Colts, but the Vikings have had only one illegal-contact penalty since then.

They have also been penalized for pass interference only twice. Hill drew an 11-yard penalty in the fourth quarter against the Texans, and Gladney got one in the end zone against Valdes-Scantling on Sunday in Green Bay, when he stumbled out of a break and hung on to the receiver’s back.