Minutes from reaching the Super Bowl last season, the Green Bay Packers brought a palpable chip-on-their-shoulder, championship-chasing attitude into the 2015 season.

After taking down Seattle in the second game, a small measure of payback for that NFC championship game loss last January, the Packers looked well on their way.

That 6-0 start was backed up by balanced performances on both sides of the ball. The inevitability of a Green Bay-New England Super Bowl became one of the NFL's early season national narratives.

More from FoxSports

Then came November.

All of a sudden, albeit after falling to unbeaten-at-the-time teams on the road in Denver and Carolina, the Packers have been vulnerable.

Aaron Rodgers has uncharacteristically missed some open receivers. Eddie Lacy has done little running the ball. The defense has softened, with no sacks in either of those consecutive defeats.

The biggest problem? That might be the Minnesota Vikings.

The Vikings used a four-game winning streak to tie the Packers at 6-2 at the season's midpoint, with critical games against each other set for Nov. 22 in Minnesota and Jan. 3 in Green Bay.

Even with their four straight NFC North titles, the reigning NFL MVP in Rodgers and half of their remaining games against losing teams, including one at home against Chicago (3-5) and two against Detroit (1-7), the Packers have found themselves in a race for the rest of the way.

Here are things to know about the NFC North for the second half of the season:

LAGGING LACY: After starting his career with a pair of 1,100-yard seasons, Lacy is on pace for barely half of that, averaging only 3.7 yards per attempt. He left the loss at Carolina with a groin injury and has been outplayed lately by backup James Starks.

Without the field-stretching, sideline-straddling abilities Jordy Nelson presented or a dynamic tight end, Rodgers and the Packers have had fewer ways to keep defenses from keying on Randall Cobb. A revival of Lacy's powerful and productive first two seasons would be a big help.

''We've definitely got to get him going,'' offensive coordinator Edgar Bennett said.

FAMILIAR FORMULA: With Adrian Peterson reintegrated into the offense, leading the league with 758 yards rushing, and the defense progressing in the second year under coach Mike Zimmer's direction, ranking second in the NFL in points allowed, the Vikings have quietly but steadily crept into contention.

They're not winning with flair, but with impeccable special teams, low penalty and turnover totals and this stingy defense, the Vikings don't need dominant quarterback play to thrive. Teddy Bridgewater has been up and down but clutch late in games and mostly protective of the ball, with six interceptions in eight games.

''We've still got a long way to go, but at least we're in the hunt,'' Zimmer said.

KEEPING PACE: The Bears have essentially started over this season with a new general manager in Ryan Pace and a new coach in John Fox, and after a rough first month the signs of advancement have begun to appear. Their past five games have been decided by three points or fewer, and they've won three of them. The return of wide receiver Alshon Jeffery from nagging leg muscle injuries has given the offense a boost.

''We believed in ourselves and believed in each other that we could do it,'' Jeffery said after a comeback victory at San Diego on Monday.

MOTOWN MESS: Jim Caldwell still has his job halfway into his second season coaching the Lions, but his future isn't exactly secure despite taking them to the playoffs last season. Team president Tom Lewand and general manager Martin Mayhew have already been fired.

''I don't walk in the spirit of fear at all in any shape or form in my life. Never have, never will,'' Caldwell said.

DOWN THE STRETCH: The Lions still have the talent to stay competitive and win a handful of games during the second half, but Caldwell's likely lame-duck status and a season-ending hip injury to linebacker DeAndre Levy ought to keep them at the forefront of the first overall draft pick derby. The Bears will try to play spoiler at Green Bay on Nov. 26 and at Minnesota on Dec. 20 and continue to give young players a long look such as running back Jeremy Langford as an eventual replacement for Matt Forte.

The Packers and Vikings? Both teams have challenging visits to Oakland (4-4) and Arizona (6-2). With a trip to Atlanta (6-2) and a game against Seattle (4-4), the Vikings have the tougher slate on the surface. But with those two head-to-head matchups with the Packers looming, they can control the race just as well as their rival.

---

Predicted order of finish: Green Bay, Minnesota, Chicago, Detroit.

---

AP NFL website: http://www.pro32.ap.org and AP NFL Twitter account: http://www.twitter.com/AP-NFL