Once-mighty teams find themselves defenseless

Ben Roethlisberger’s numbers are up across the board, and he’s completing a career-best 68.3% of his passes . . . but the Pittsburgh Steelers have lost five in a row and essentially have bumbled their way out of playoff contention.

Tom Brady directs the AFC’s top-ranked offense, and he ranks near the top in most positive statistical categories . . . but the New England Patriots have lost three of their last five games.

Eli Manning is on pace for his first 4,000-yard passing season, and is coming off a career-best 391-yard game . . . but the New York Giants have lost six of eight and no longer control their postseason destiny.

There are two things to note in all of this:

* The mighty have fallen . . . or at least have taken a big step back.

* Don’t blame the offense.

The Patriots, Steelers and/or Giants have been in seven of the last nine Super Bowls, winning all but one of those. This fall, however, each is faced with serious defensive problems that have bubbled to the surface in the second half of the season.

That’s not to say the offenses have been ideal, far from it. But the defensive breakdowns, particularly in the passing game, have been the undoing for these teams -- even if the statistics don’t reflect it. They’re all ranked among the top 11 defenses.

A look at what’s gone wrong:

Giants

New York built a 5-0 record mostly on fluff teams -- those opponents are now a combined 20-45 -- and what was supposed to be one of the league’s best pass rushes got an unrealistic view of what it could do.

Sure, the Giants had five sacks against Kansas City and six against Oakland, but New York has just 12 in the last eight games.

The players up front aren’t getting to quarterbacks, and that puts additional pressure on a secondary that hasn’t been able to recover from the Week 3 loss of safety Kenny Phillips, a rising star. There are no playmakers in that secondary, and the communication breakdowns are constant.

What’s more, the team has gotten very little return from the huge investment it made in the off-season in defensive free agents Chris Canty, Rocky Bernard and Michael Boley.

Patriots

Although they’re still atop the AFC East, the Patriots have yet to show they can win close games the way they have so routinely in the Brady era. It doesn’t help that they’ve lost so many veteran leaders on defense -- Tedy Bruschi, Mike Vrabel, Richard Seymour, Rodney Harrison -- and linebacker Jerod Mayo (last season’s defensive rookie of the year) hasn’t returned to form since suffering a knee injury in Week 1.

A turning-point moment this season came when Bill Belichick decided to go for it on fourth down at Indianapolis, when the Patriots were protecting a lead and were deep in their territory. After the Colts won that game, Belichick came under fire for not having faith in his defense.

Then again, considering the way the Patriots’ defense played in a 38-17 loss at New Orleans, can anyone blame the coach?

A glaring weakness has been New England’s inability to generate a pass rush. Free-agent linebacker Derrick Burgess has been a big disappointment; he has three sacks, one more than rookie safety Patrick Chung. Jarvis Green, Seymour’s longtime backup, got his first sack of the season last week.

As is the case with the Giants, there have been frequent communication breakdowns in the secondary -- so much so that Belichick has simplified the system so as not to avoid a complete coverage meltdown.

If there’s any doubt that teams feel comfortable throwing against the Patriots, consider this: The run-based Miami Dolphins let second-year quarterback Chad Henne throw 52 times in beating them. That’s not a good sign.

Steelers

The No. 1 mantra of defensive guru Dick LeBeau is “Don’t give up the big play.” For years, the Steelers have adhered to that. Not this season.

The franchise that led the NFL a year ago by allowing just two completions longer than 40 yards has given up seven this season, five during the current losing streak.

Pittsburgh is getting decent pass pressure -- though surprisingly little from star linebacker James Harrison lately -- but has suffered all sorts of short-circuits in communication.

Clearly, losing All-Pro safety Troy Polamalu was a crippling blow, and no one has stepped into that play-making void. Harrison, the defending defensive player of the year, had forced four fumbles in the first five games but none in the last eight. He has not had a sack in the last three games.

That’s not to say blame should be heaped on Harrison, but he hasn’t been the impact player he was last season. And he’s not alone on that defense.

It’s unimaginable that the Steelers would give up three fourth-quarter touchdowns to the Raiders at home. But they did.

And four days later, the defending Super Bowl champions lost at Cleveland, looking completely deflated, disinterested, disoriented, defeated.

So many Ds. So little D.

sam.farmer@latimes.com

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