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Kamil Krzaczynski-USA TODAY Sports

Longtime veterans are no stranger to the NFL's biggest stages. Just ask Tom Brady, who won his latest Super Bowl at 43; or Aaron Rodgers, who at 37 is fresh off at two straight NFC Championship Game appearances. But football is very much a young man's game, too. That's why we're identifying players on their rookie contracts who are key to the success of their respective teams in 2021. Right here, we're focusing specifically on the NFC North, where the Bears, Lions, Packers and Vikings will go head to head.

Here are which youngsters matter most to each of the NFC North foes:

Bears: QB Justin Fields

Player experience: first season
How acquired: 2021 draft (No. 11 overall)

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Justin Fields Getty Images

It doesn't get much simpler than this. Chicago may be touting Andy Dalton as its scheduled Week 1 starter, but you don't move up in the first round for a quarterback if you don't expect him to take over sooner rather than later. Turning to the bigger, better Fields won't be enough to guarantee the Bears a return to the playoffs (the offensive line, wide receiver and secondary depth are all legitimate concerns). But it sure as heck should get them closer to exciting fans and challenging opponents. Fields was added to be the future in Chicago, but he's also easily the biggest X factor of the present. Whether or not he emerges and/or thrives quickly could determine the fate of not only the Bears in 2021 but the team's leadership structure beyond it.

Lions: OT Penei Sewell

Player experience: first season
How acquired: 2021 draft (No. 7 overall)

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Penei Sewell Getty Images

The Lions could make do without Sewell if they bumped Halapoulivaati Vaitai back to right tackle, and their other starters up front -- Taylor Decker and Frank Ragnow, in particular -- are better than they get credit for. But with Jared Goff set to take over under center as a reclamation project/stopgap QB, nothing is more important in Detroit than a sturdy O-line. Of course it might not matter regardless, considering Goff will be throwing to the likes of Tyrell Williams and Breshad Perriman, but this is a QB especially dependent on a comfortable pocket. The only way the Lions are going to surprise in 2021 is if Goff somehow rekindles some of the poise and magic of his Rams peak, and that means getting immediate protection from Sewell as a bookend.

Packers: C Josh Myers

Player experience: first season
How acquired: 2021 draft (No. 62 overall)

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Josh Myers Getty Images

Let's start by noting that this would look different in the event Aaron Rodgers actually holds out, hangs up the cleats and/or forces a trade elsewhere: In that scenario, second-year QB Jordan Love would instantly become the obvious X factor of the 2021 season. Should Rodgers return, however, Myers holds arguably more sway over Green Bay's chances than any other rookie-deal player. Why? Because the Packers are trusting him to immediately take over for All-Pro center Corey Linsley. You could make a case for rookie cornerback Eric Stokes since Jaire Alexander is the only proven steady hand at that spot, or other young pieces like Amari Rodgers and Darnell Savage, but Myers will be responsible for protecting either Rodgers, Love or some other QB out of the gate.

Vikings: OT Christian Darrisaw

Player experience: first season
How acquired: 2021 draft (No. 23 overall)

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Christian Darrisaw Getty Images

Second-year receiver Justin Jefferson is already a star, and we trust that he's a safe bet to produce again in 2021. Tight end Irv Smith Jr. is also an underrated X factor considering he could be Kirk Cousins' new No. 3 target after finally taking over for Kyle Rudolph. As is corner Cameron Dantzler, who faces slightly less pressure now that Patrick Peterson and Bashaud Breeland are in town. That leaves Darrisaw, a gem of a first-round find who's set to step in for the departed Riley Reiff right away. Are we expecting too much of a seamless transition for Darrisaw, who'll be charged with keeping Cousins upright in an important year for the veteran QB? The rookie just has to be solid to successfully replace Reiff, but if he falters early, it could disrupt the Vikings' entire offense.