Late this summer, a New England Patriots official jokingly asserted that the franchise’s biggest problem during training camp was handling so many questions about whether they would go undefeated.

The defending champions were not only a favorite to repeat, they were on a different plane from the rest of the NFL, a franchise with its own gravitational pull. There was the Patriots, and there were the 31 teams chasing them.

A quarter of the way through the season, late summer seems like the distant past for the Patriots. In a span of four games, the central question of their season has shifted in unthinkable fashion. It is not, can they make it through the season without a loss? It is, can they make it through another week without embarrassing themselves?

Embarrassing – there is not another word for New England’s defense after four games. The Patriots are 2-2, tied with the New York Jets and a game behind the Buffalo Bills in the AFC East. They have yielded 32 points per game, more than any team in the NFL, and uniformly turned opposing quarterbacks into All-Pros.

The best simple measure of a quarterback’s performance might be yards per attempt. Against the Patriots this season, quarterbacks have posted 9.4 yards per attempt. That total that would have led the league every season since 2000 – no active quarterback has passed for 9.4 yards per attempt over a full season. Last year, MVP Matt Ryan punched up 9.3 yards per attempt. Aaron Rodgers’s career high is 9.2. Tom Brady’s is 8.6.

The Patriots have a defense incapable of going undefeated, defending a Super Bowl, or even winning a division. New England’s defense, in a word, stinks.

The hallmark of Coach Bill Belichick’s defenses is discipline. This season, the Patriots have been busted for big plays with alarming frequency. On Sunday, Carolina’s Cam Newton threw two touchdown passes to wide receivers who would not have been more open in pregame warm-ups.

The Patriots also lack an impact pass rusher. Quarterbacks are averaging 3.1 seconds to throw against the Patriots, the highest figure in the NFL (the league average is 2.7 seconds). New England lost Rob Ninkovich to retirement and tried to replace him with Kony Ealy and rookie Derek Rivers. Ealy was such a poor fit they waived him before Week 1, and Rivers suffered a season-ending knee injury in camp. They traded with the Seahawks for Cassius Marsh, who hasn’t worked, either. Trey Flowers and Deatrich Wise have shown glimpses, but no consistency.

The trades of Chandler Jones and Jamie Collins were both justified, but the Patriots have yet to make up for the loss of their athleticism and playmaking. Now, the Patriots are primed to make another trade. It’s unclear how much one deal can help a defense this bad.

Then again, the Patriots may not be as far off as their performance has shown. Aside from Ninkovich, the only two starters missing from last year’s Super Bowl are cornerback Logan Ryan (free agency) and linebacker Shea McClellin (injured reserve). Key defensive lineman Jabaal Sheard is also gone. But missing those four should not ruin a defense so severely. The Patriots have a little less talent, and their new players haven’t grasped Belichick’s system. Those two factors have created a defensive disaster.

The Patriots are lucky to be 2-2. A week earlier, Brady bailed out the defense with a last-minute touchdown drive, made possible only when Texans Coach Bill O’Brien kicked a field goal rather than trying for a game-clinching conversation on fourth and a foot.

The Patriots’ other problem is that the Bills might actually be good. Buffalo is 3-1 under first-year head coach Sean McDermott after upsetting the Falcons and becoming the first team to win in Atlanta since Week 13 last year. The Bills have wins against Denver and Atlanta, a pair of 3-1 teams. Buffalo’s only loss came at Carolina, when it held the Panthers to nine points and saw a potential winning touchdown sail through wide receiver Zay Jones’ hands in the final seconds.

The Patriots have little time to address what is wrong. They will travel to Tampa Bay to face the Buccaneers on Thursday night.

Belichick has a knack for solving thorny problems. It would be unwise to believe he can’t fix even this Patriots defense, be it through a personnel upgrade, adjustments or coaching points. The unit only has to be serviceable – Brady is again playing at a superhuman level.

Right now, the defense is wasting another vintage Brady season. The Patriots have serious problems, bigger than anyone could have seen coming this summer.