Two friends become bitter rivals on Sunday at TCF Bank Stadium — for a few hours, at least.

Jay Gruden and Mike Zimmer — both of whom served together on the Cincinnati Bengals' coaching staff from 2010 to 2012 — will be pitted against each other for the first time as NFL head coaches, as Gruden's Redskins take on Zimmer's Vikings at 1 p.m. in Minneapolis.

Zimmer, who served as defensive coordinator in Cincinnati while Gruden served as offensive coordinator, said it's not easy preparing to play against one of your friends and former coworkers.

"You know, I like Jay an awful lot," Zimmer said this week in a conference call with the D.C.-area media. "We are friends; we worked together for two years. You know, really I don't like play against my friends."

In Cincinnati, the duo – under the watchful eye of head coach Marvin Lewis – helped to guide the Bengals to three-consecutive playoff appearance and the 2013 AFC North Championship.

Now at the helm of their own franchises, both squads enter the contest 3-5 and the strength-on-strength matchups stem from the minds of their head coaches: the Vikings' defense vs. the Redskins' offense.

Through the first eight games, Washington's offense ranks seventh in yards per game (391.9) and fifth in pass yards per game (289.5).

After turning the Bengals offense into one of the more productive units in the NFL, Zimmer's not shocked that Gruden has done the same so far in D.C.

"Their team is very well-coached, playing great on defense," Zimmer said. "He has always done a great job with the quarterbacks, he has done a great with the offense, I think the receivers love playing for him and has got a good running game."

Likewise, Zimmer has turned the Vikings defense into one of the best in football after a forgettable performance just a year ago.

After Minnesota ranked 31st in the NFL in defense (397.6 yards per game) last season, Zimmer has turned them into a top-10 team in 2014, ranking eighth in yards allowed up per game (323.8) and fourth in pass yards allowed per game (212.1).

While the turnaround has been significant, Gruden isn't surprised what Zimmer has been able to achieve with his defense.

"He's very demanding of his players. He demands greatness from his defense," Gruden said. "You watch the tape and he's taking that defense who struggled a little bit last year into one of the top five or six defenses this year and a lot of it is because of his scheme."

Gruden said he can remember several clashes on the practice field against Zimmer while with the Bengals, as the two coaches tried to get their units ready to battle together on Sundays.

Now, that chess match carries over onto opposite sidelines — but this time they'll get the chance to shake hands after it's all said and done.

"We competed every day in practice," Gruden recalled. "It was not friendly, usually. Both of us are pretty good competitors and we all wanted to win the drill, definitely – in Cincinnati – so we had our share of arguments and tension, but ultimately I have a ton of respect for him."

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