Mike Zimmer and Andy Reid have spent a combined 53 NFL seasons on opposite sides of the football.

Zimmer, 63, is the old-school but innovative defensive guy whose aggressive style impresses the 61-year-old Reid. Reid, meanwhile, is a true 20th century West Coast offense disciple who Zimmer lauds for changing with the times to maximize the misdirection benefits of offensive football in the 21st century.

Sunday, Zimmer’s 6-2 Vikings, winners of four in a row and ranked third in scoring defense (16.5), travel to play Reid’s 5-3 Chiefs, losers of three consecutive home games but ranked fourth in scoring (28.3) and looking at the outside possibility of quarterback and reigning league MVP Patrick Mahomes returning from a knee injury.

Zimmer vs. Reid. A tangible matchup because even as head coaches, these two have maintained tight grips on their play-calling duties. As head coaches, Reid and Zimmer have done it since 1999 and 2014, respectively.

So, fellas, which is harder to do? Offense or defense?

“I have a lot of thoughts on that,” Zimmer said with a sly smile.

Any you care to share publicly, Mike?

“Well,” he said, “if it doesn’t work on offense, you can punt. If it doesn’t work on defense, they raise their hands like that.”

Zimmer made the touchdown signal and laughed.

What say you, Andy?

“I think it’s probably a challenge either way,” Reid said. “But it’s something that if you asked both of us, we’d say it’s the most fun we have.”

That’s it? No vote? C’mon, Andy. Zim cast a firm yes for his side.

“All right,” Reid said. “That’s OK. You know … no comment.”

Reid was laughing as he said that. He and Zimmer have been crossing paths since 1986 when Reid was offensive line coach at Northern Arizona and Zimmer was coaching defensive backs at Weber State. Recently, they’ve served together on the NFL coaches subcommittee.

“Andy has always been a great coach,” Zimmer said. “He’s always been a hard guy to defend. He’s actually changed a little bit. He used to be true West Coast. Now it’s a lot of RPOs [run-pass options] and four guys out on a side and things like that.”

The Chiefs rank No. 1 in the league in RPO percentage, according to Zimmer. They’re second in the league in yards per play (6.57) and first in yards after the catch (1,335).

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VideoVideo (01:49): Vikings wide receiver Stefon Diggs says the offense has proved itself to be able to put points on the board.

After losing to the Eagles in the NFC Championship Game two seasons ago, the Vikings defense spent the offseason focusing on the proper ways to read and react to RPOs. Their knowledge will be tested Sunday, especially if Mahomes plays.

“The RPO is the new-age triple option,” defensive end Stephen Weatherly said. “Where the old-school triple option was either running back, quarterback or pitch option, this one is run left or throw right. Your defense is going in two separate directions.

“You need discipline because RPOs really bring that old-school stress back to a new-age defense. Hey, that’s a good line, isn’t it?”

Yes. And so is mixing old- and new-school labels to describe Reid, who ranks sixth in NFL history with 212 career wins (200-127 in the regular season and 12-14 in the playoffs).

Hopes of Reid winning his first Super Bowl increases with each game Mahomes plays. Asked Wednesday to name his starting quarterback for Sunday, Reid joked, “We just made a trade …” before adding, “I don’t know. We’re just taking it day by day.”

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VideoVideo (02:25): Sunday's game against Kansas City has the potential to be high scoring, and Vikings running back Dalvin Cook says Minnesota will need to execute on every drive to keep pace.

Reid said Mahomes would do “a little more” in Wednesday’s practice but still would be limited. His backup is Matt Moore, 0-1 after losing 31-24 to Green Bay at home last week, out of football last year and signed in September only because Chad Henne got injured.

Zimmer has needed extra prep time this week to forge two different sets of defensive calls based on the two quarterbacks.

“Facing Mahomes in, for instance, the RPOs, we know he can be more on the move and throw it across his body,” Weatherly said. “They always tell quarterbacks not to throw across their body. Well, he has the arm to do it, so he does. That means you have to cover everyone on the field for the whole play. Him being in the game is different than any other quarterback in the league running RPOs.”

Reid, meanwhile, must prepare for a veteran defense that’s talented and finely tuned after years in Zimmer’s scheme.

“Mike does a great job,” Reid said. “We’ve gotten closer since we’ve been on this [coaches subcommittee]. He told me he wasn’t going to blitz one time this game. I said that’s fine.”

Reid laughed, knowing full well how long Zimmer has been attacking guys like him from the opposite side of the football.