Mike Zimmer is sitting, but certainly not relaxing, inside his new office at Winter Park. It's late April, two weeks before the NFL draft and three months before his first training camp, and he is taking time off his already-hectic schedule to convince a visitor that he didn't do all the work during the many reclamation projects he oversaw in two decades in the NFL.

"I want them to have a love for football," Zimmer said. "But I think most football players want to get better at what they do."

The table in front of him is cluttered with schedules and thick binders and a plastic bottle for tobacco juice. His cellphone, inside a case with a camo design, sits on the table, too. Scribbled on a whiteboard in the corner are a couple of blitzes. The visitor presumes those will involve a little bit of camouflage, too.

"The guys that haven't gotten better," Zimmer continues, "it's because they have something really holding them back, whether it's something off the field or maybe they're not ready to buy in or they think they're better than what they are. I try not to give them too much of an opportunity to not believe that they can better. I'm pretty hardheaded."

Sunday, 4½ months of fixing later, Zimmer will unveil the new-look Vikings defense for the first time in a game that counts, the season opener against the St. Louis Rams. Zimmer's roster renovation is far from complete, but the 58-year-old first-time head coach showed in previous posts that he knows a thing or two about getting the most out of the defensive talent he has.

One thing is for sure: Those who have played for and worked with Zimmer in the past expect his Vikings defenders to be focused and prepared so they can play fast and physical.

"You look at Pete Carroll and what they're doing in Seattle, I think that's the mentality," former Cowboys safety Darren Woodson said. "He wants to be in your face with that punch-you-in-the-mouth type of mentality."

In people's faces

When Zimmer arrived in Dallas in 1994 to coach defensive backs for new head coach Barry Switzer, the Cowboys were coming off consecutive Super Bowl titles. Switzer's predecessor, Jimmy Johnson, built a frenetic defense around players who were a tad undersized but fast as all heck. The Cowboys had ranked in the top five in points allowed in 1992 and 1993.

"We had just won two rings and had a very good football team and a very good secondary, and he did not back down," said Woodson, now an analyst for ESPN. "Zim came in and instantly was in our faces."

Woodson, who went to the first of his five Pro Bowls that year, said Zimmer's film sessions were uncomfortable. If the cameras caught you blowing an assignment or jogging to the ball, Zimmer would rewind it over and over and over again.

"If you're going to play for Mike Zimmer, you better have thick skin," Woodson says now, laughing.

While coaching a secondary led by Woodson and Hall of Fame cornerback Deion Sanders, Zimmer worked in lockstep with defensive coordinator Dave Campo. Woodson said Zimmer often installed the game plans, and together Zimmer and Campo kept the Cowboys a top-10 unit for the rest of the decade.

"We didn't have a lot of talent," Woodson said. "In '95 and '96, man, our drafts were terrible. But he put in some wrinkles that made it hard for opponents to exploit our weakness."

Zimmer was promoted to defensive coordinator in 2000 and kept the job after Bill Parcells, another of Zimmer's current-day mentors, replaced Campo as head coach in 2003. The Dallas defense clicked that season, leading the league in yards allowed and ranking second in scoring defense.

"We weren't more talented than anybody else, but we had smart guys and they did everything right," Zimmer said.

Rebounding in Cincy

When Parcells retired after the 2006 season, Zimmer headed to Atlanta to join Bobby Petrino's first staff there.

That 2007 season was a disaster for the Falcons, with quarterback Michael Vick going to prison on dogfighting charges and Petrino sneaking out the door with three games left to coach at Arkansas. The Falcons finished 29th in total defense and scoring defense.

"It was really hard to just focus on football," said free-agent safety Chris Crocker, who played for Zimmer as a member of the Falcons, Bengals and Vikings. "There were a lot of distractions. It was just like one thing after another that season, but I think he had us going in the right direction."

It didn't take long for Zimmer to land on his feet. Marvin Lewis, who extensively studied Zimmer's Cowboys while designing a Ravens defense that in 2000 had one of the stingiest seasons ever, brought in Zimmer to take over the Bengals defense.

"Mike had a great command of everything, from the front to the back, and that was important to me," Lewis said. "As a coach, you don't ever want to rebuild in the NFL. You get one year, and that's your first year. Other than that, you're not rebuilding anything. You've got to win and win now."

In 2008, the Bengals climbed from 27th in the league in total defense to 12th. Over the next five seasons, they ranked seventh or better four times and made the playoffs in each of those seasons.

Lewis, the head coach, provided input on everything from overall defensive philosophy to gameday decisions, but for the most part it was Zimmer's show. He changed the terminology. He improved the players' preparation habits. And perhaps most important, he and Lewis rebuilt the roster.

"Everybody started with a clean slate, and then we were going to coach the hell out of them," Lewis said. "I'm sure Mike would say the same thing about Minnesota now. If you don't want to be coached, then you need to go to another club."

Together, they helped youngsters such as defensive tackle Geno Atkins and defensive end Michael Johnson become stars. They took cornerbacks Terence Newman and Adam Jones off the scrap heap and fixed some of their flaws. And they took a chance on an undrafted linebacker named Vontaze Burfict, who led the league in tackles last season.

"[Zimmer] does a great job of putting together a game plan that creates problems for what you want to do," said LSU offensive coordinator Cam Cameron, who had a few frustrating afternoons coaching against Zimmer when he was with the Ravens. "He was able to help them when they weren't that talented. Then all the sudden they started drafting really, really good players and signing good free agents. That's when that defense really took off."

Instantly aggressive

Zimmer's scheme has evolved throughout his 20 years in the NFL. His coverage principles have changed, with him calling for more man concepts after coaching Sanders with the Cowboys. His experiences with Parcells' 3-4 fronts in Dallas have made his fronts more multiple. And the explosion of NFL passing attacks has forced him to come up with clever nickel defenses. But his core philosophies remain intact.

"Some of the things haven't changed in 20 years," Zimmer said.

Zimmer is now scheming up another turnaround, for a Vikings defense that allowed an NFL-high 480 points in 2013 and surrendered 37 passing touchdowns, one of the highest totals in league history.

Zimmer has repeatedly said that he is not concerned with how individual defenders performed last season in the Cover-2 defense that former Vikings head coach Leslie Frazier preferred.

"Overall, he has an aggressive mentality, which doesn't mean he's just going to blitz, blitz, blitz, but he definitely believes in being aggressive when the situation calls for it. He's not a read-and-react type of coach," NFL Films senior producer Greg Cosell said. "Every time I watched Cincinnati, it seemed like they had more free rushers to the quarterback than maybe any team in the league,"

On third-down plays, Zimmer often crowded the line of scrimmage with 10 defenders, including seven inside the hashmarks. The key, though, is the two linebackers he puts in the A gaps on both sides of the center. The last thing an offense wants is quick pressure up the middle, so it must slide protections inside, creating confusion and favorable 1-on-1 matchups on the edges.

Zimmer wasn't the pioneer of the concept, but he was one of the first coaches to do it regularly.

In the preseason, Zimmer's defense gave quarterbacks fits with that blitz package. And at times during his four preseason wins, his defense perhaps provided a glimpse of what could be a bright future. The Vikings flirted with shutouts in two of their games while ranking second in the league with 12.2 points allowed per game.

But a lot of work still must be done for Zimmer to finish fixing another broken defense.

"To be a top-10 defensive football team, you have to be good in pass defense, you have to be able to rush the quarterback, you have to be good on third downs and you have to be able to stop the run and try to make the quarterback one-dimensional," Zimmer said last month. "So I am not happy but probably satisfied with the progress of where we are. I am never happy."