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Sam Shields arrived in Green Bay, Wisconsin, in 2010 as an undrafted free agent. After three seasons at the University of Miami (Florida) as a receiver, Shields made the switch to defensive back.

While not possessing great height, his arm length and athletic scores made it appear as though he'd have a promising future. For those reasons, Rivals.com ranked him ahead of future NFL receivers like Kenny Britt, Jeremy Maclin, Hakeem Nicks, and Demaryius Thomas during the high school recruiting process.

The undrafted free agent stunned the league with his early performance, keeping his spot on the team. When Charles Woodson slowly phased out of his starting cornerback role to a hybrid safety, Sam Shields entered the starting lineup on a more consistent basis. He played well enough for the Packers to fork over a four-year $39 million contract this past offseason.

With an elevated salary in pocket, Shields should be able to compete head-to-head with the big boys in the league and hold his own. His paychecks signify that, if nothing else. Against the Chicago Bears, that was put to the test. Resembling more a basketball team than receiving unit, the two featured Bears in the catching game are Pro Bowlers Alshon Jeffery and Brandon Marshall.

The tandem together totaled 58 yards through the air during the game. That's a much lower statistic than the 111-yard, 95-yard and 142-yard totals in the three previous weeks of this season.

How were the Packers able to keep that number down on Sunday? A lot of the result had to do with Shields and his ability to win at the catch point against the Pro Bowl pair.

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Here, the Packers were backed up against their own end zone. To the short side of the field was Davon House, a rotational cornerback, covering Brandon Marshall. At the bottom of the screen was Alshon Jeffery, who lined up across from Sam Shields.

With no help over the top, Shields and the Packers clearly let the Bears know it's man coverage. With the big frame of Jeffery, Jay Cutler made the pre-snap decision to test the defensive back, hoping for a resulting score.

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Shields' first step was to open his hips, allowing Jeffery outside. The last thing the Packers wanted was to make the throw shorter, so by forcing him outside, it makes Culter do a more difficult pass. By giving up the inside, Shields would also be allowing an open passing lane to Jeffery, as there would have been no one between the passer and the target.

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With the receiving background in his blood, Shields knows to keep his eyes on the ball. Instead of playing his man, he rides out the route on him but keeps his eyes in the backfield to time the play he'll need to make on the ball to prevent a score.

"Getting your head around" is an important trait for young cornerbacks. Many high draft picks who bust at that position fail because they lack the skill to diagnose where the ball is.

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While Jeffery was able to leap ahead of Shields when attacking the ball, it didn't stop the former Hurricane to get a hand on it. The Bears' target is clearly physically larger than the corner, but Shields' arm length allows him to get a hand on the ball, breaking up the pass in the end zone.

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This is another time in which Shields is in man coverage with no one to help over the top. With the second quarter dying down, the Packers are willing to give underneath passes to the Bears, which will eat up the clock.

Chicago, though, wanted to drive for more than just a handful of yards at a time. This is evident with the route that Jeffery, lined up at the top of the screen, would run: a streak with a back-shoulder element.

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Again opening up his hips early in coverage, Shields and the Packers made and executed the idea to force the ball into a smaller area for Culter. With Jeffery pinned between the sideline and Shields, the margin of error became very small.

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With the back-shoulder break made, the Packer again explodes toward the ball and got his hand on it for a deflection. Twice the Bears had Shields on an island, and twice he came up with a positive high-impact play for Green Bay.

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With Shields reading the backfield so often, it allows him to make plays on balls that have clearly misfired too. This play, for example, was a bad read by Marshall. While he ran deep, Cutler threw a route well under the receiver. Shields, able to react quickly, made a play for the ball for the wide-open interception.

On Shields int, Trestman said Marshall was supposed to run a hook. Ran a go, Cutler threw the hook, game over. Marshall didn't talk after. — Tyler Dunne (@TyDunne) September 28, 2014

The eye issue does goes both ways, though. While it's a trait, it's not one without consequences. At times, teams will take advantage of aggressive eyes of a defensive back.

Wait wait packer fans you can't be surprised sam shields lost his man by taking his eyes off him, happens every week — leroy butler (@leap36) September 28, 2014

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Previously in the game, the Bears had moved Jeffery in a deep motion near the end zone. Following him in full sprint was Sam Shields. That was the bait. The play above is trap.

Jeffery comes in motion then breaks back straight to the left sideline from where he originally came. The slot target, Marshall, has an inside-breaking route, which created a large vacated space for Jeffery to get open and run in if Shields completely bailed the area.

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When Jeffery broke to the sideline, Shields was near the center of the field still continuing to the opposite sideline. He had lost his man in the pursuit of reading the backfield.

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By the time the throw finally came to fruition, the play looked like an obvious touchdown to even the least-trained eye in Soldier Field. With no one between him and the end zone, Jeffery was going to score.

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Sprinting in an attempt to makeup for his mistakes, Shields does become the closest Packer to make a play, but even his speed wasn't enough.

Final Thoughts

Sam Shields will return to Green Bay this week with a couple big plays made in Chicago under his belt. His eyes fixated on the backfield are both a blessing and a curse. He may break on interceptions that others don't see or time a deflection at the catch point at the correct time, but he also will be keyed on when cheating with the same aggressive eyes.

For a player like that, you have to take the good with the bad and hope it's mostly good. Against Chicago, it's fair to say the Packers and Shields were mostly good covering All-Pro receiving talents. The Packers, on any day, would love to see the Shields who performed on Sunday against the Bears in every game.