The best way to illustrate how lightly opposing offenses regard the Patriots pass rush came on the first play of the fourth quarter of Sunday's 22-21 loss to the Dolphins.

Miami, starting a drive at its own 3-yard line, didn’t turn around and hand the ball to running back Ricky Williams, its most reliable offensive option and the traditional play so close to its own end zone.

Instead, trailing by two late in a key divisional game, they threw the ball, allowing quarterback Chad Henne to drop back — without the protection of his starting center — under the shadow of his own goal post without fearing a potential safety.

Of course, Henne wasn’t hit. Instead, he completed a 10-yard pass to receiver Greg Camarillo, allowing the Dolphins offense to get some breathing room and providing the latest example of just how far the New England pass rush has fallen.

To say the Patriots have had problems generating sustained pressure on the quarterback is kind. This year’s team has just 20 sacks through 12 games, and is in danger of setting an ignominious new low under Bill Belichick. Only one Belichick-coached Patriots team since 2000 has finished with less than 30 sacks as a team — the 2000 team had 29. The 2009 team is on pace to finish with 27. (By way of comparison, the 2007 Patriots had 47 sacks.)

After an offseason in which the Pats lost defenders Richard Seymour (who tied a career-high in sacks last season with eight) and Mike Vrabel (who had four last year, but had a career-best 12.5 in 2007), New England is tied for 28th in the league with 20 sacks as a team — only Houston (19 sacks), Kansas City (17) and Jacksonville (12) have had less success getting to the quarterback than the Patriots.

Outside linebacker/defensive end Tully Banta-Cain leads the Patriots with 5.5 sacks, while defensive lineman Mike Wright has four. Linebacker Adalius Thomas, who has been used more in coverage than in his traditional pass-rushing role this year, has three, while OLB/DE hybrid Derrick Burgess, who the Patriots acquired in exchange for a third- and fifth-round pick from the Raiders before the start of the season, has two sacks.

When it comes to getting pressure, some of New England’s recent ineffectiveness is due to playing a lot of nickel defense against pass-happy teams such as the Colts and the Saints — chances are good that even the best pass rushers won’t make much of a dent when there are extra defensive backs dropping back into coverage.

But on Sunday against the Dolphins, New England spent most of the afternoon operating in its base 3-4 defense, and Henne was never outside of his comfort zone. The Patriots got to him once, with Banta-Cain and Jerod Mayo sharing a sack midway through the first quarter. But other than that, New England had zero success in getting pressure on Henne — the quarterback dropped back to pass a career-high 52 times and was only sacked once.

“I don’t know,” responded Thomas when he was asked about the lack of a consistent pass rush after Sunday’s game. “You have to ask somebody that does that study or whatever. Whatever they call, that’s what we play.’’

Belichick, who constantly preaches team defense, says it’s not solely the fault of the pass rush. Pressure on the quarterback and good coverage go hand in hand, and when you fall short in one department, chances are good that the other areas will suffer.

And so when cornerbacks Darius Butler, Jonathan Wilhite and Leigh Bodden struggle in coverage — as they did on Sunday — it creates a domino effect. As a result, the Dolphins as a team were 12-for-22 on third and fourth down on Sunday.

“Pass rush and pass coverage are totally interrelated,” he said. “[Sunday], we obviously didn’t do a good enough job on third down and that hurt us, especially in the first half — two or three on fourth down or whatever it was. A combination of third and fourth down, that was an area that we didn’t perform as well in as we needed to.”