EAGAN, Minn. -- Mike Zimmer thinks about it all the time. What would his life be like as a coach if he decided to hand over playcalling duties once and for all?

It’s a decision he says he grapples with every day. Only once in his five seasons in Minnesota has Zimmer not called the plays for his defense. On Dec. 1, 2016, Zimmer was forced to miss the Vikings’ game against the Dallas Cowboys after undergoing emergency surgery on his right eye. In his place, defensive coordinator George Edwards called plays while special teams coordinator Mike Priefer filled in as head coach. Even in a two-point loss, the Vikings became the first team to hold the Cowboys’ offense under 300 yards during the 2016 season.

“I think about it every day,” Zimmer said about whether to give up playcalling duties. “Just trying to do two roles is hard, and they haven’t doubled my pay any.”

Mike Zimmer can't bring himself to turn over the defensive playcalling duties for the Vikings. Brace Hemmelgarn/USA TODAY Sports

In a league where many head coaches carry an offensive background, Zimmer is the lone head coach still in charge of calling defensive plays, a job that’s “a pain in the rear end,” the 62-year-old joked. Giving up those duties would afford him more time to focus on in-game management, perfecting his ability to master the clock, timeouts and the situations he puts his team in, like whether to take an intentional safety and/or the critical decisions he faces in the final minutes of each half.

But despite how much is on his plate, Zimmer hasn’t been able to pull himself away from the job he has been responsible for since he first became a defensive coordinator in Dallas in 2000.

“Typically, I think I do a good job on Sundays adjusting to the game,” Zimmer said. “I had a coach tell me one time, the first quarter is about your game plan, the second and third quarter are about making adjustments and the fourth quarter is about doing the best things to win the game. And so for me, I’ve kind of done this for a long time now that I can see a lot of things that are hurting us and try to adjust it, try to get it back under control.

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“The other thing is, I don’t want to be a second-guessing coach. I have a style of how I call a game, and George, even though he tries to do it like I do it, I don’t want to tell him, ‘I hate that call,’ or he should have called this. I don’t think that’s fair to him. If I want something called, I should call it.”

Juggling two strenuous roles requires immense balance, but also finding the right person to handle playcalling on the other side of the ball. In February, the Vikings hired John DeFilippo, a one-time playcaller for Cleveland, heralded as one of the bright up-and-coming offensive minds in the NFL.

The coach Zimmer faces off with on Thursday’s matchup of NFC heavyweights knows that well. When Sean McVay was hired by the Rams in 2017, he brought Wade Phillips on staff as his DC, knowing his team’s defensive playcalling was in good hands with Phillips’ 41 years of NFL experience.

“I think the biggest thing that you feel so good about is that you have great people around you that you can lean on and you can work through stuff,” McVay said. “I think while you are the head coach, we do things as a coaching staff, as an organization, and there's a lot of people that are involved in our decision making. That's what I feel so fortunate about, is being able to lean on people. You have such confidence in the defensive staff, and the special teams coaches to do an excellent job. If you are a little bit more involved with the offensive staff, those guys do a great job if I'm not around.”

At 29 years old, during his second year as the offensive coordinator in Washington in 2015, McVay was handed offensive playcalling duties by Jay Gruden.

Sean McVay trusts his experienced defensive staff led by Wade Phillips while he focuses on the offense. Joe Nicholson/USA TODAY Sports

It was a job he felt he was ready for. Then reality set in of all the challenges that would entail.

"You always think you can do it, then you get into it, and you realize it's a lot more humbling than you realize," McVay said. "You make mistakes, you try to learn from those, and that's when you realize that when you're around great people that kind of invest and mentor you, you can learn and kind of accelerate your career."

For two seasons in Washington, McVay was responsible for calling plays for Kirk Cousins, elevating his game to reach its highest level in 2016 while orchestrating one of the league’s premier passing attacks. Upon arrival in Los Angeles, McVay helped reshape the trajectory for Jared Goff and Todd Gurley during their second year in the league.

McVay views game day as a collaborative group effort. While he's on the field calling plays, Jedd Fisch, a senior offensive assistant, is up in the booth overseeing clock management operations throughout the game. They have direct contact to each other in game, and the responsibilities delegated to Fisch allow McVay to focus his efforts on executing what's on his play sheet.

"I just think that we lean heavily on our staff, whether that’s calling plays where you’re leaning on the dialogue that exists between the offensive staff throughout the course of the game," McVay said.

There’s a push and a pull in trying to do everything, and juggling both roles is difficult. During the preseason, Zimmer handed over playcalling to Edwards for several games, giving himself the chance to test out the emphasis he has made on situational football and in-game management before the regular season.

For McVay, who calls plays for the fourth-best offense in the NFL, and Zimmer, whose vaunted defense rose to No. 1 in multiple areas last season, that learning curve is always in motion, no matter how long they’ve each been calling plays.

“It's constantly just trying to balance it out,” McVay said. “I think it's really all about the efficiency every single day, but you never want to do anything -- if you are going to be involved in the offense like that -- that takes away from being a good playcaller. How you balance that as a head coach is something that I'm continuing to learn on the fly, but having great people around you helps ease that transition."