By Chris Emma–

INDIANAPOLIS (CBS) — Put in the most simplistic form, NFL teams are either trending upward or downward.

Countless variables factor into such an equation, from team ownership and management all the way down the roster. Teams trending upward generally have a core of players in place, an established regime or a new one rebuilding. Those trending downward have crumbling infrastructures and problems poised to crash down.

One could argue that as presently constructed, each of the NFC North’s four teams is trending upward.

“It’s a heck of a division,” Vikings coach Mike Zimmer said Thursday at the NFL Combine.

Zimmer’s Vikings have a third-year quarterback Teddy Bridgewater and one of the NFL’s most promising defenses. With Anthony Barr, Harrison Smith, Everson Griffen and more, Minnesota is poised to contend for the playoffs every season for some time to come.

Meanwhile, the Packers have been the gold standard of the NFC North ever since its revision in 2002, winning the division title eight times in 14 seasons. Mike McCarthy has a Super Bowl ring and established success, though Green Bay’s run of three straight division crowns was ended abruptly by Minnesota in 2015.

Detroit is the only team to never win the NFC North crown, last winning the division as the NFC Central in 1993. The team’s moving forward with a new general manager in Bob Quinn, formerly a product of the Patriots’ front office. Despite the potential retirement of superstar receiver Calvin Johnson, the Lions have enough team talent to compete.

Finishing last place in 2015 were the Bears, a team that made a one-win improvement in John Fox’s first season as coach. When training camp in Bourbonnais arrives, the Bears will have a vastly different look to their roster, with approximately $60 million in cap space and nine draft picks at general manager Ryan Pace’s disposal.

“Really, the next three months, we have a great opportunity to significantly improve our team,” Pace said. “I’m looking forward to it.”

Added Fox: “This is about evaluating and decision-making. We need to do very well this offseason.”

The laws of football logic would suggest that four teams can’t coexist vying for a winning record and playoff spot, barring some extremely odd scenarios. Something has to give, and someone has to fail.

The Packers scuffled for a stretch last season, finishing 10-6 after a 6-0 start to the season. They lost at historic Lambeau Field to each of their division rivals for the first time in decades, an indication of that divisional parity. Still, Green Bay managed to beat Washington in the wild-card round before falling to Arizona. This was a team that had Super Bowl potential in place.

“We’re a solid team,” Packers general manager Ted Thompson said. “We’ve got good players at places where you need good players. I don’t think we have a lot of weaknesses. I think we’re going to be a competitive team for time to come.”

The NFC North’s favorites in 2015 will be the Packers and Vikings, with each boasting outstanding skill players and collective depth. Having Aaron Rodgers and Adrian Peterson doesn’t hurt, either.

If the Lions can maximize their talent and minimize the mistakes of quarterback Matthew Stafford, it’s a team that can make noise too. Coach Jim Caldwell led Detroit to the playoffs in 2014, with much of that same core in place.

Pace and his Bears brass could have a say in this, with the opportunity to completely revamp the roster with younger, better players. Finishing 6-10 with so many replacement-level players was a credit to those coaches and evaluators employed at Halas Hall, but they’ll admit it wasn’t close to good enough.

So, what happens? Not every divisional team can be in the playoffs.

With each of the NFC North’s four teams seeming to be moving in the right direction, what’s going to give?

“Our division is as tough as ever,” McCarthy said. “In particular this year, it could be our toughest.”

Chris Emma covers the Chicago sports scene and more for CBSChicago.com. Follow him on Twitter @CEmma670 and like his Facebook page.