Just four weeks ago, we were wondering about the odds of the New England Patriots getting through the 2017 regular season undefeated. It felt justified. Last year's Super Bowl champs appeared to have gotten better this offseason.

Now, with just a quarter of the season played, New England is 2-2 and has a serious flaw on the defensive side of the ball.

Entering Week 4, the Patriots had the worst defense in the league by our Net Expected Points (NEP) metric, which is adjusted for strength of schedule. New England ranked 32nd in Adjusted Defensive NEP per play, coming in 31st against the pass and 25th versus the run.

After a then-surprising loss to the Kansas City Chiefs in Week 1, New England’s offense was able to overcome the team's defensive deficiencies against the New Orleans Saints and Houston Texans. But against the Carolina Panthers, the defensive struggles were too much.

Miscommunication

New England allowed the Carolina offense to get on track after entering the game with the 23rd-ranked offense by Adjusted NEP per play. Cam Newton had been out of sync with the offense through the first three weeks of the season, but Newton put up the second-best quarterback performance of the week by Passing NEP per drop back.

Overall, the Patriots allowed the second-most NEP per play of any defense in Week 4 (counting the Thursday and Sunday games) -- it was the most until the Indianapolis Colts imploded in the second half against the Seattle Seahawks on Sunday night. The Colts had only the 20th-ranked defense by Adjusted Defensive NEP per play heading into the week, so it’s likely the Patriots stay ranked dead last through the league’s first month.

Against the Panthers, it wasn’t just that the Pats were executing poorly. There were breakdowns and miscommunications all over the field, perhaps none bigger than on Carolina’s last drive of the first half. The Patriots allowed a 43-yard completion to a wide open Kelvin Benjamin on a 3rd-and-9, a play which alone boosted Carolina’s chances of winning the game by 9.85 percent, per numberFire Live.

Benjamin was left alone after a stacked release. The play was also set up by motion from Christian McCaffrey from the backfield to the outside. All of Carolina’s routes went to the right, except for Benjamin’s, which broke to the left. From the stack, both Eric Rowe (25) and Stephon Gilmore (24) followed Russell Shepard and the rest of the offense to the right, which left Benjamin alone.

Two plays later, the Panthers scored on a 10-yard pass to Devin Funchess. Again, motion created miscommunication for the Patriots. Funchess motioned from left to right and while he was followed across the formation by Rowe, Gilmore waved him off. That led to more talk between Rowe and Devin McCourty (32) up until the snap. The result of the talk was no one covering Funchess in the end zone.

As a general rule, when three defenders flail their hands at each other right before the play, good things generally don't happen.

The touchdown increased Carolina’s win expectancy another 8.09 percent, with a net of 19 percent on the nine-play, 84-yard drive. The score also gave the Panthers a 17-13 lead, one they didn't give up until a New England field goal with 3:09 left that tied the game at 30. Carolina was able to drive down the field and kick a field goal of their own to win the game as time expired.

Throwing At Will

Big plays have been a problem for New England. So far, the Pats have allowed 22 plays of at least 20 yards on defense, the third-most in the league behind the Saints and Colts. Last season ,New England allowed just 56 all year, the 11th-fewest.

Through four weeks, no defense has allowed a higher percentage of touchdowns (7.7 percent) and a higher yards per attempt average (9.4) than New England. The next closest team to the Patriots’ yards per attempt figure is the Saints at 8.6. Right now, opposing quarterbacks have been turned into 2017 Tom Brady against this defense...almost.

The Patriots know how nice it is to have Tom Brady under center. This year, they’ve been sharing the love.

On top of the secondary, a lot of blame is being placed on the defensive line. Some of it is deserved -- New England has sacked opposing quarterbacks on just 5.3 percent of drop backs so far, the fifth-lowest rate in the league. They also haven’t generated much pressure to force bad throws. Per Sports Info Solutions charting from Football Outsiders, New England came into the week with the sixth-lowest pressure rate on defense at just 24 percent.

These deficiencies aren’t exactly new. Last year, the Patriots had a 5.3 percent sack rate across the whole season, which ranked 18th. They also had a 24.8 percent pressure rate, which ranked 23rd. With little production up front, the Patriots still finished 11th in Adjusted Defensive NEP per play in 2016, due in part to an 11th-ranked pass defense.

Future Outlook

There’s some reason for hope on this defense. The Patriots invested in secondary help with the addition of Gilmore, and though it’s been rough at the start, there’s talent there. This is also a Bill Belichick team, which makes it hard to believe the communication problems before and during plays will continue.

The question, though, is how long will it take to fix these problems. New England has a quick turnaround, as they face the Tampa Bay Buccaneers (13th in Adjusted Passing NEP per play through Week 3) on Thursday night. After that, they get the New York Jets (20th) before home games against the Atlanta Falcons (8th) and the Los Angeles Chargers (11th) preceding their bye.

That’s not an easy stretch, and how quickly the defense gets fixed could determine whether or not the Patriots are a serious contender in 2017.