The first quarter of the 2017 NFL season has not exactly gone as planned. The Rams, Eagles and Bills find themselves unexpectedly in sole possession of first place, while the Jaguars and Lions are tied atop their respective divisions.

What did we learn from all of Sunday’s games? Here are five takeaways from Week 4:

New England’s defense could prevent the Patriots from repeating 

The Patriots’ defense is officially a problem. New England's record dropped to 2-2 Sunday with their 33-30 loss at home to Carolina, putting them in a tie for second place in the AFC East. Once the heavy Super Bowl favorite, it’d be hard to make the argument that the Patriots are the best team in football.

The 42 points that New England gave up in the season opener weren’t much of an aberration. The defending champs have surrendered at least 33 points in three of their four games. The Panthers had one of the NFL’s worst offenses in the first three weeks of the season, yet facing New England was all Cam Newton needed to return to his MVP form. The Patriots rank dead last in total defense, and only six teams in NFL history have allowed more yards over the first four weeks of a season. The 128 points allowed in four games is the most for a New England defense in franchise history.

New England’s defense can’t be this bad all year long. They gave up fewer points than any team a season ago, and Bill Belichick should find a way to make the unit improve. But Tom Brady and the offense can’t win a Super Bowl by themselves, and the Patriots could have trouble in the playoffs if their defense costs them a first-round bye.

The Rams and Bills are legitimate playoff contenders

As two of the NFL’s worst teams in 2016, it’s clear that Los Angeles and Buffalo have taken a significant step forward in 2017. Even if winning their respective divisions isn’t in the cards, the Rams and Bills should both, at the very least, be in the race for a wild-card spot for most of the season.

L.A. made a statement with their 35-30 win in Dallas, defeating the team that had the NFC’s best record last year. While the Rams had been impressive in their previous two wins, it was their first victory over a good team, and it came on the road. Leading the NFL with 35.5 points per game, Los Angeles has proven that their offense is for real. Jared Goff and his 112.2 passer rating look every bit like a former No.1 overall draft pick, and Todd Gurley is one of the league’s top playmakers. The Rams have a chance to take complete control of the NFC West when they host the Seahawks in Week 5.

It’s doubtful that anyone outside of Buffalo believes the Bills will stay in first place for much longer, but Sunday’s win in Atlanta was validation that the team’s defense is one of the league’s best. After allowing 16 points or fewer in their first three games, Buffalo shut down the reigning MVP at home in a 23-17 win over the Falcons. Even before Julio Jones left the game with an injury, Atlanta was having trouble moving the ball in their own building. With opponents like the Jets, Dolphins, Bengals, Chargers and Colts left on their schedule, Buffalo could be in the hunt for a postseason berth until Week 17.

The Browns are still the Browns

The idea that Cleveland might actually give teams some trouble this season went by the wayside pretty quickly. After suffering a third straight loss to a mediocre opponent, it’s evident that 2017 is going to be another long year for the Browns.

Entering Week 4 with a winless record, Cincinnati looked like a playoff team in their trip to Cleveland Sunday. The Browns allowed Andy Dalton to be nearly perfect in the 31-7 loss, and DeShone Kizer had another bad outing before being replaced by Kevin Hogan in garbage time. Cleveland was thoroughly outplayed in Week 3 when they lost to the Colts, and their Week 2 loss in Baltimore wasn’t close. No.1 overall draft pick Myles Garrett still hasn’t gotten on the field, and Kizer has been the NFL’s worst starting quarterback, giving Cleveland fans few reasons to be positive each week.

If the Browns can’t win at home against the Jets in Week 5, things could get ugly very quickly. It might not be too long before talk of another 0-16 season starts up again.

Don’t try to predict the AFC South

The NFL’s worst division has now become the league’s most unpredictable division. The Jaguars, Texans and Titans are all tied with a 2-2 record with a seemingly similar chance to end the season in first place.

In Week 1, it was Jacksonville blowing out the Texans in Houston. Seven days later, Tennessee won easily in Jacksonville. Sunday was Houston’s turn as they beat the Titans 57-14. Maybe the Texans are now the favorite with the emergence of Deshaun Watson, though Sunday was the first time that he posted a truly impressive passer rating. Marcus Mariota’s hamstring injury could have a major effect on things going forward, though it might not be serious. The Jaguars’ defense is good enough to win the division, but Blake Bortles remains an issue.

As long as Andrew Luck is sidelined, the Colts aren’t a threat in the AFC South. Indianapolis has lost two games by at least 28 points, and they could be essentially eliminated from contention if they can’t beat Tennessee or Jacksonville in their two upcoming division games.

Pittsburgh will run away with the AFC North

This doesn’t come as much of a shock. The Steelers began the season considered to be the biggest threat to the Patriots by many, and they are the only divisional favorite that sits alone in first place after four weeks.

Baltimore blew their chance to prove they could offer Pittsburgh a real challenge with Sunday’s 26-9 loss at home to the Steelers. As impressive as the Ravens’ defense has been at times, their offense isn’t nearly good enough to compete for the AFC North crown. Cincinnati isn’t winning the division after losing their first three games, and Cleveland is an afterthought. Pittsburgh still hasn’t come close to playing their best football of the season, and they’ll build a sizeable first-place lead if that happens soon.

The Steelers’ defense has been impressive, allowing no more than 18 points in regulation in any game. Pittsburgh is a much better team at home, and they’ve got seven games remaining at Heinz Field.