The Patriots are facing a problem that some believe should have them panicked

For the fourth week in a row, the New England Patriots defense was shredded by an opponent, sending the team to a surprising 2-2 start.

Not long ago, there was talk of a 19-0 season for a Patriots team that looked stacked at every angle - perhaps no one could stop them from running to another Super Bowl win.

Then the Kansas City Chiefs shredded the Patriots for 42 points in a season-opening loss. In Weeks 2 and 3, the Patriots out-dueled the New Orleans Saints and Houston Texans while giving up a combined 53 points. And on Sunday, the Patriots fell 33-30 to Cam Newton and a Carolina Panthers team that had been struggling mightily on offense.

It's become clear the Patriots have issues on defense. As ESPN analyst and former quarterback Tim Hasselbeck said on WEEI's "Kirk and Callahan," the defensive issues should have the team "panicked."

"Everyone has got to be panicked inside that building," Hasselbeck said. "In year's past, it seems so many games weren't even competitive. These weren't closely decided football games. If you're looking at it now, it's like, 'Wait a minute, here.'"

Hasselbeck continued: "By and large, New England wins those close ones because they're more prepared and better coached. But it doesn't seem like that when you watch them on defense. It really doesn't."

The problems are multi-tiered. As SB Nation's Christian D'Andrea noted, the Patriots still haven't found viable replacements for Chandler Jones and Jamie Collins, two excellent versatile defenders they traded away on the brink of new contracts. Likewise, they were hit by injuries to key players like Dont'a Hightower and random events like the retirement of defensive end Rob Ninkovich during training camp.

Other issues, like schemes and communication are there, too. A commonly noted example from Week 4 was when three Patriots followed Panthers running back Christian McCaffrey in motion, while running back Fozzy Whitaker broke free for what became a 28-yard touchdown.

And as Ben Volin of the Boston Globe noted, Cam Newton had other options.

Here's the play:

Cornerback Stephon Gillmore, one of the Patriots' biggest offseason acquisitions and reason for optimism, blamed himself after the game, saying: "It's frustrating when it's communication, it's not really ability. I have to get better at the communication part. It's my fault on the communication."

Safety Devin McCourty said of the Patriots' defense: "It's bad. We're letting the team down."

As some have noted, it's not the first time there has been cause for concern about the Patriots after Week 4. In 2014, after Tom Brady was benched in a blowout loss to the Kansas City Chiefs, some wondered whether it was the end of the Brady-Bill Belichick era as the team fell to 2-2. The Patriots soon bounced back and won the Super Bowl that year.

Last year, concerns about the defense arose when the Seattle Seahawks poured 31 points on the Patriots in Foxborough. The Patriots would eventually finish 16th, exactly average, in defensive DVOA. And, of course, they won the Super Bowl.

It may not be beneficial to get completely up in arms about the Patriots' defense, but there are reasons to be worried. A lack of dominant pass-rushers has left what was supposed to be a strong secondary to be exposed.

Also of concern is how dominant Tom Brady has been through four weeks. The Patriots have also scored 126 points through four weeks and Brady is yet to throw an interception. As dominant as Brady is normally, he's having one of the best starts to a season of his career - at 40. A regression, no matter how slight, is likely, meaning the Patriots will need the defense to step up even more when the offense does slow down.

With such fundamental flaws in personnel, the Patriots will have to rely on coaching to turn this around. Belichick and company have earned the reputation for fixing holes on the team, but through four weeks, it looks like a huge challenge.