The secondary was supposed to be a strength for New England this season.
It's been anything but.
Cam Newton became the fourth straight quarterback to torch the Patriots for more than 300 yards on Sunday, leading Carolina to a 33-30 win over the defending Super Bowl champions (2-2), whose two losses have both come at home.
The 2015 league MVP had been struggling to find his passing rhythm this season and hadn't thrown for over 200 yards in a game.
But on Sunday, he completed 22 of 29 throws for 316 yards and three touchdowns, with one interception. Five completions went for more than 20 yards.
Newton made a several good throws, but more often than not, he found receivers that were wide open because of a broken coverage.
His first touchdown, a screen pass to Fozzy Whittaker in the second quarter, went for 28 yards after cornerback Stephon Gilmore followed running back Christian McCaffrey in motion and left the entire left side of the field open.
"We're beating ourselves," said cornerback Malcolm Butler. "We lost the game ourselves. It was nothing Carolina (3-1) was doing. Basically, we beat ourselves, blown coverages, penalties."
Gilmore drew two of the biggest flags, both for hands to the face.
The first extended the opening drive of the second half that gave the Panthers a 23-16 lead.
The second, on the game's final drive, wiped out a sack by Deatrich Wise Jr. that would have made it fourth down on the Panthers 16-yard line. Carolina ended up driving 49 yards in six plays to set up Graham Gano's game-winning 48-yard field goal.
Gilmore, who signed a five-year $65 million contract in the offseason, said he was just playing aggressive defense.
"I don't know what else I can do," he said. "I just jammed him in the chest. It just happened to go up to his neck area and the ref called it."
Gilmore was expected to be an upgrade from Logan Ryan, who signed as a free agent with Tennessee. But the defensive backs acknowledge there has been a chemistry issue and a lack of communication that the unit did not suffer from a year ago.
In the first four games, the Patriots defense has given up an average of 457 yards, 324 through the air.
"It's not like we don't go over this stuff in practice," said safety Duron Harmon. "It's obviously something we need to work a little harder at. Obviously what we're doing is not good enough."
And Gilmore hasn't been the only star to play poorly.
Butler gave up a key pass interference penalty in the end zone of the season opener, and ended up losing his starting job for a week. Devin McCourty was beaten twice last week for touchdowns by Texans rookie quarterback Deshaun Watson.
"I wouldn't even say anybody's new anymore," McCourty said. "It's tough to still be talking about new guys and, `This guy's gone.' And honestly, It doesn't matter. I think we've all played together long enough."
There were a few bright spots on defense. Butler made his first interception of the season and linebacker Dont'a Hightower returned after missing two weeks with a knee injury. He had two tackles and a sack.
The most shocking statistic for the Patriots may be 1-2, their record at home this season. The two losses are as many as the team had all of last season. Quarterback Tom Brady, who was suspended for last year's loss to Buffalo, hasn't lost two at home since 2012.
"At the end of the day, it's not really where you play," said Brady, who brought the team back from a 30-16 deficit with two fourth-quarter touchdown drives. "It's how you play and road, home, night, day, 1 o'clock, 4'o'clock, it's really how you play. We just haven't done a great job putting together four quarters of football."
Especially on defense.