As much as Vikings backup quarterbacks Sean Mannion and Jake Browning put forth admirable efforts this week at TCO Performance Center, they are not Seahawks quarterback and MVP candidate Russell Wilson.

So, linebacker Anthony Barr has gotten creative with how he practices "spying," or shadowing, mobile quarterbacks. He's the Vikings' main operative, called upon in the instances they need to mirror whichever athletic passer they're facing that week so he doesn't run on them. The list of targets has "grown" this season, Barr said, including every NFC North quarterback, Cowboys quarterback Dak Prescott and, likely during Monday night's game, Wilson.

But improving as a spy in the NFL takes time.

"It's hard," Barr said, "because no one is going to impersonate Russ and what he does. Our quarterbacks do as best a job as they can as far as getting out and giving us that look."

Browning, the 23-year-old undrafted rookie out of Washington, was told to run around as best he could leading the scout-team offense during practices this week.

"He's a unique one with all the scrambling he does," Browning said of Wilson. "The one thing is he's scrambling looking to throw deep. It's a little different than Lamar Jackson, where he's scrambling looking to run. It's a different challenge, just trying to give the defense a good look."

Barr's eyes have made him a better spy by his sixth Vikings season. He can't practice tackling Wilson or knowing when he'll pump fake, but Barr works on timing by toying with offensive linemen and scout-team quarterbacks. He'll stare down a receiver, selling man-to-man coverage before the snap. As soon as the lineman and/or passer turns his helmet away, he'll close on the quarterback.

The spy role, as Barr described, is really a "second-level defense." The job also changes hands. Eagles linebacker Nigel Bradham and safety Malcolm Jenkins spied Wilson during moments of Philadelphia's 17-9 loss to Seattle last weekend.

"Sometimes it's a defensive lineman," head coach Mike Zimmer said. "Sometimes it's a DB, sometimes it's a linebacker. It just varies."

The defensive line fronts the first level, and on any given snap the pass-rush plan could call for a fence around Wilson or direct pressure to one spot flushing him to an opening they're waiting to close — perhaps with the spy.

That approach helped the Vikings defense limit Wilson to a career-low 72 passing yards in last year's 21-7 loss at CenturyLink Field.

"There was always somebody," Barr said, "a D-linemen or spy, responsible for getting that second-level defense on Russell. We rushed as a team. That's what you have to do against him."

There's an "art" to the spy, said linebacker Eric Kendricks. You must maintain the proper distance and angles, and don't get caught. Offensive linemen are trained to grab spies when they recognize them, preventing a Barr or Kendricks from mirroring the quarterback across the line of scrimmage. More often, according to Kendricks, the spy is just trying to prevent a run and force a bad throw or throwaway.

It's a direct response to the quarterback. Vikings coaches may enter Monday night's game prepared to put a spy on Wilson every third-and-long situation, but if Wilson decides not to leave the pocket all night, they'll rush or drop another defender.

Or, in the case of the Nov. 17 win against the Broncos, defenders entered with little concern over quarterback Brandon Allen's mobility. But when Allen started buying time with his legs during a 20-0 lead at halftime, they pivoted.

"OK, now we have to start spying him," Barr said.

Barr was also a spy on the most well-known play of his career when he hit Packers quarterback Aaron Rodgers on Oct. 15, 2017. Rodgers landed on his throwing shoulder and suffered a broken collarbone, all but ending his season.

"That was an unfortunate play," Barr said. "You want to get there as fast as possible and buy time for the [defensive] backs to make sure they don't have to cover for too long. That's what really hurts you, when a guy gets out of the pocket and receivers are running all over."