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A year ago, when the Vikings signed Alex Boone to a four-year, $26.8 million contract on the first day of free agency, they billed the guard as something of an emblem for their rebuilt offensive line.

Boone would bring a dose of toughness to a group that badly needed it, the Vikings said. He would join new offensive line coach Tony Sparano and excel in the physical style of run blocking the coach would bring with him from San Francisco.

Eighteen months and 14 regular-season games later, the 6-foot-7 Boone is gone, having been released Saturday in the Vikings' final wave of roster cuts. After refusing a pay cut, and after the team's unsuccessful attempt to trade Boone, according to multiple sources, the 30-year-old was let go for $3.3 million in cap savings (along with $3.4 million in dead money). And while the Vikings will start an ex-49ers lineman on Monday night, it will be Nick Easton — the player they used for five starts last season after trading for him in 2015.

So what happened to change the landscape for the former prized free agent? Well, a lot.

Let's start with the sea change the Vikings have undergone on offense since signing Boone: Teddy Bridgewater sustained a catastrophic knee injury, precipitating a trade for Sam Bradford. Adrian Peterson tore his right meniscus, rendering moot the downhill power runs that offensive coordinator Norv Turner favored and Boone relished. And after Turner resigned in the middle of last season, the Vikings turned the offense over to Pat Shurmur — Bradford's coordinator in St. Louis and Philadelphia who favored more West Coast offensive principles and a zone-running scheme.

What's the difference? Rather than relying on powerful offensive linemen such as Boone to move large chunks of earth, zone schemes lean more on quick, mobile linemen who can work as a unit and create opportunities for running backs to make one cut up the middle of the field, bend a run outside or bounce it back into a cutback lane.

"These guys are a little bit more athletic; they don't need to be as big," said ESPN NFL analyst Herm Edwards, who spent eight years as a head coach for the Jets and Chiefs. "They're not the big heavy guys that are double-teaming. They're more, 'When the ball is snapped, get off the ball — then use your momentum as you try to stay in your gap to push you out of it, because everything is going sideways.' Nothing is going vertical, it's all sideways."

The Vikings implemented plenty of zone runs in Peterson's heyday, capitalizing on the running back's ineffable cutback ability. Now, they will use them for Dalvin Cook, the running back they drafted in the second round out of Florida State. It was a zone scheme that helped Cook set a school rushing record as a Seminole, and it's part of the reason why the Vikings saw him as such a good fit for their offense.

"He came from a pretty advanced offensive system at Florida State," Shurmur said in training camp. "You saw principles of zone running, gap running and pass protection where he was involved. He was also involved in route running. He has a pretty good foundation of what we're going to ask him to do, and I think that helps him."

If the shift helped Cook, there's little doubt it hurt Boone, who seemed to struggle with the changed responsibilities. When he missed the Vikings' second preseason game in Seattle, it gave the team an opportunity to play Easton at left guard and rookie Pat Elflein at center. By the team's final preseason game on Thursday night, there were whispers that Boone's spot in the lineup could be on tenuous footing.

That's generally a bad spot for a 30-year-old guard making $6.7 million to be in the NFL. And while the move will register as one that delivered an underwhelming return on a significant investment, it is perhaps, more than anything, a sign that the aftershocks from the Vikings' seismic offensive shift of 2016 still are reverberating.