EDEN PRAIRIE, Minn. -- The partnership began with a bold stroke: Mike Zimmer, first-time NFL head coach at age 58, would bring in three-time head man Norv Turner to run the Minnesota Vikings' offense, help guide their search for a franchise quarterback and serve as an ex-officio head coach of sorts who could aid in Zimmer's transition from defensive coordinator to football CEO.

Zimmer was lauded for being comfortable enough in his own skin to bring in a coordinator of Turner's renown, and the two, along with Vikings general manager Rick Spielman and quarterbacks coach Scott Turner, spent their first months together conducting a quarterback search that landed on Louisville's Teddy Bridgewater.

The partnership's coda was as striking as its opening notes: Norv Turner resigned Wednesday morning after the Vikings' upset loss to the Chicago Bears on Monday night, in a move Zimmer said was both surprising and not demanded by the head coach. Both Zimmer and Turner spoke warmly of each other, saying they'd remain friends, and Zimmer said Scott Turner would remain as quarterbacks coach. There were rumblings long before Wednesday, though, that the partnership's days could be numbered.

After the 2014 season, Zimmer approached Hue Jackson -- his former colleague with the Cincinnati Bengals -- to pick his brain on offensive philosophy, so Zimmer could evaluate his own offense from a more educated perspective, according to a league source. He was more vocal about offensive strategy during the 2015 season, saying after the Vikings' 23-20 loss to the Arizona Cardinals in December that he didn't like Turner's play call on the final play of the game and agreeing with Adrian Peterson following a December loss to the Seattle Seahawks that the Vikings should have run the ball more. When the Vikings replaced offensive line coach Jeff Davidson with Tony Sparano -- a former head coach and Zimmer's longtime associate in Dallas -- they canceled an interview with Pat Flaherty, the former New York Giants offensive line coach who'd started his NFL career with Turner.

The Vikings' decision to bring in Pat Shurmur (who became the Vikings' interim offensive coordinator on Wednesday) signaled Zimmer was looking for a broader base of ideas after the team had ranked 29th in offense last season.

Even before Shurmur was brought on board, it would have been overly simplistic to call the Vikings' attack a carbon copy of Turner's longstanding Air Coryell offense; they'd incorporated more of the short passes that Bridgewater preferred, spent nearly two-thirds of their time in the shotgun after Bridgewater became the starter in 2014 and had even dabbled in some West Coast offense-based concepts last season. Bridgewater had tried to find his voice in the offensive game plan last season; Zimmer said in December he wanted Bridgewater to be more assertive about what he liked and didn't like in the offense, adding that there were times where the coach would relay Bridgewater's preferences to the offensive staff, rather than Bridgewater doing so directly.

The shifts in the Vikings' offense this season -- some planned, some brought about by the circumstances of a wild year -- left their attack looking even more like something Shurmur had designed than what Turner had long used. Spielman said Shurmur was instrumental in the decision to trade for Sam Bradford after Bridgewater's knee injury, and as the Vikings readied Bradford to start just 15 days after he was traded from the Philadelphia Eagles, they centered on some of the concepts he'd run with Shurmur in Philadelphia, incorporating quick throws (particularly to Cordarrelle Patterson, whose marginalization in 2014 and 2015 had puzzled some in the organization) and run-pass options into the offense while adding a dash of Sparano's Wildcat sets to the mix.

"Pat was also instrumental in bringing [Bradford] here, knowing him and knowing what kind of person he was and what his qualities are," Zimmer said last month. "Also, they’re able to talk and communicate. One good thing about Sam is that when we start talking about gameplan and stuff he’ll say that I’m not comfortable with that play and we won’t run it. So, I think the combination of the coaches and him worked and the things he’s done helped."

When Turner resigned Wednesday, he told ESPN's Ed Werder that "I think we just have different views on where the offense is going." Told of Werder's report, Zimmer said, "I would not describe that [as accurate]. I would say that since Norv has been here, I’ve given him almost 100 percent, total free will in everything that they’ve done offensively. Obviously I’ll come in and make suggestions, but there really has never been a time I have demanded anything from there.

"We talked for a long time about a lot of things, and I told him my feelings for him and how much that I respect him and things that he has done and he has continued to do and how hard he’s trying to get it going. He was pretty set in his ideas and his reasons, and I hope that we always continue to be friends."

Turner's contract was up after 2016, and there was a growing belief this year would be his last with the Vikings. Still, though, Zimmer said he was not planning to make a change, and added the 64-year-old Turner described the move to him as a resignation, not a retirement.

As Turner departs, he leaves behind an offense that looked much different than the one that made him famous. The metamorphosis, for a team that has long tried to match its scheme with its parts, figures to continue.