A month ago, the NFC North looked like potentially the toughest division in football. The Green Bay Packers had the league’s best quarterback, Aaron Rodgers. The Minnesota Vikings had the NFL’s top defense. The Detroit Lions had, arguably, the top special-teams unit and the Chicago Bears had just traded for Khalil Mack, one of the league’s best defensive playmakers.

Yet three weeks in, the division looks like a big jumble with no undefeated teams and the surprising Bears at 2-1. There’s still plenty of time, of course, for this to play out. But three weeks in, what has changed? What’s to be believed and what will still come across as a falsehood by the end of the season?

Khalil Mack had a memorable Bears debut against Aaron Rodgers and the Packers in Week 1. Jeff Hanisch/USA TODAY Sports

How has the impact of Khalil Mack changed your outlook on the division race?

Courtney Cronin, ESPN Vikings reporter: The Bears' defense has legitimized their playoff hopes in 2018. A team that felt like it was still a year away before Sept. 1 is now in first place in the NFC North, thanks in part to how the acquisition of Mack has taken this unit to another level. Every team is now circling the Bears on their calendar, wondering how the heck they’re going to block the former defensive player of the year who has recorded a sack and forced a fumble in three straight games. This defense is advancing at such a rapid rate that the only thing that could halt Chicago’s chances at the playoffs might be its play at quarterback. The long and short of it: There’s no longer a two-team race in the division between the Vikings and Packers.

Rob Demovsky, ESPN Packers reporter: Let’s see the Bears shut down an elite quarterback before we declare them real players in the NFC North -- even with a dominant pass-rusher like Mack. They couldn’t keep Rodgers from finishing them off in the opener, and that collapse could end up being costly. They beat Russell Wilson, who is solid but not elite and the Cardinals played two quarterbacks by choice, which means they don’t really have one. Talk to me after Week 7 when they play Tom Brady, and then we’ll see.

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Michael Rothstein, ESPN Lions reporter: It’s huge. Fans (and media, too) often overlook the true impact of defensive stars in the league now because of the intense focus on fantasy and offensive skill players. But Mack has made Chicago one of the league’s most dangerous defenses and is such an impact playmaker. He has forced a fumble in every game this season. He has four sacks in three games. And for opposing offensive tackles, there really is no easy way to handle him. He changes protection schemes and will only get better as the season goes along and he begins to understand his NFC North opponents. In my opinion, bringing Mack in should end up giving the Bears at least two more wins this season than they would have had without him.

Kevin Seifert, NFL writer: The only position that can change the course of a game more than an elite pass-rusher is an elite quarterback. So, sure, the Bears' acquisition of Mack changed my outlook. It gave the Bears arguably the best defense in the division, a pretty important asset when you're competing with Rodgers, Kirk Cousins and Matthew Stafford. Through three weeks, the Bears rank No. 8 in scoring defense (18.3 points per game) and No. 1 in ESPN defensive efficiency. In the end, the trade elevated the Bears into equal contention with the Vikings and Packers.

More concerning start, Packers or Vikings?

Cronin: The fact that there wasn’t just one area that plagued the Vikings against the Bills, but breakdowns across the board, was alarming. We knew the offensive line might struggle to find its footing, but no one expected that unit to give up a league-high 29 pressures to Buffalo. We knew it might take Kirk Cousins a couple of games to feel fully comfortable in the offense (though he showed no issues with that in his heroic fourth-quarter/overtime comeback at Green Bay), but his field vision vs. the Bills was a far cry from when it has been at its best. And the issues on defense constantly stemming from “miscommunications” where players are being left uncovered to run free between linebackers and cornerbacks has been a problem in each game. The best-case scenario is that the Buffalo game was a blip on the radar. The worst case is that it’s a sign of issues that will continue to arise.

Kirk Cousins and the Vikings suffered through an embarrassing loss to the Bills at home in Week 3. Bruce Kluckhohn/AP Photo

Demovsky: The Vikings, by virtue of their loss at home to the Bills, should be a little more concerned about their 1-1-1 start. At least the Packers haven’t lost one at Lambeau yet. Yes, the Packers’ showing against the Redskins was ugly, but it was on the road in the rain, and perhaps the Redskins will turn out to be a playoff contender. Minnesota probably needed to be better than 1-1-1 heading into perhaps their most difficult stretch with consecutive road games at the Rams and Eagles coming up. The Packers have a chance to get on top with easier games against the Bills, Lions and 49ers next up. But it gets much harder for the Packers after that.

Rothstein: The Packers, no question. While the Vikings' being annihilated by the Bills was surely surprising, it felt to me like just one of those days and not something to be worried about long term. Green Bay, meanwhile, has some legit concerns and it starts with Rodgers' injured left knee. We’ve all seen what happens to the Packers minus Rodgers by looking back to last season. That he’s playing hurt this early in the year gives me more pause for how Green Bay might hold up throughout the season. The Packers' defense, though, adds to the concern, particularly with Muhammad Wilkerson out. The Packers are last in the division in yards allowed per game (386.7), passing yards per game (262.3), sacks (six) and interception percentage (1.9). Teams are also driving well on them (20.7 first downs allowed per game). Rodgers or not, those are numbers to be worried about.

Seifert: Vikings. Plenty of warning signs have already emerged. They've already had to replace their kicker after he cost them a game. Top running back Dalvin Cook, who missed 12 games last season because of a torn ACL, is dealing with leg issues once again. And they've indefinitely lost team captain and top pass-rusher Everson Griffen as he undergoes a mental evaluation. And that's only three weeks' worth of stuff! The Packers have had their struggles as well, but in terms of quality of play, a loss at Washington seems less alarming than getting blown out at home by the Bills, as the Vikings were last week.

Who is the favorite to win the division?

Cronin: The Vikings and Packers are still the favorites, but I’ll stick with the Green Bay pick I made in July. Green Bay and Minnesota’s Week 12 rematch could serve as the tiebreaker for the division after their 29-29 OT tie in Week 2, and I think in the meantime, the Packers' schedule over the next three weeks (Bills, at Lions, 49ers) sets them up more favorably than the Vikings' stretch of back-to-back road games at the Rams and Eagles before finally coming home to play the Cardinals. If Minnesota ends the first five games at 1-3-1, that could be very difficult to overcome on the way to an NFC North title.

Demovsky: It sure looked like whoever won the Week 2 game between the Packers and Vikings would be favorites in the NFC, but, of course, they tied. Wouldn’t it be nice to fast-forward to Nov. 25 when the two teams play again at U.S. Bank Stadium? The guess is that the Packers go into that game at either 6-3-1 or 5-4-1. The same is probably true for the Vikings, making the Week 12 game in Minneapolis a possible tiebreaker in the NFC North. Both could still end up as playoff teams, but you have to wonder if that tie will end up costing one of them a wild-card spot.

Rothstein: Went with Minnesota in the preseason. Sticking with Minnesota now. The Vikings have a tough stretch coming up playing at the Rams on Thursday and then the next week against Philadelphia. But I won’t worry too much about the Vikings unless something happens in Week 6 (Arizona) or Week 7 (at Jets) that is unexpected. Defense still matters, and Minnesota has one of the league’s best. And the offense, save the terrible start against Buffalo, has looked strong with Cousins completing 68.3 percent of his passes with seven touchdowns and two interceptions. It’s still the Vikings at the top. It’s what happens behind Minnesota that will have a lot of intrigue the rest of the way.

Seifert: Packers. If in doubt, I always pick the team with the best quarterback. Again, the Packers have their issues. Their deep pass defense has been especially weak. They're giving up an average of 7.08 yards per dropback, the eighth highest in the league. But if it comes down to a battle between the Vikings' ominous start, the Lions' inconsistent play and a team with Mitch Trubisky at quarterback, I'll take Rodgers and the Packers. We've seen many examples of Rodgers' ability to navigate the Packers through races they would have no business being in without him.