By Tony Massarotti, Globe Staff

The No. 1 seed in the AFC entirely in their grasp, the Patriots return to the field tomorrow against the Miami Dolphins. The Houston Texans already have lost again. The Pittsburgh Steelers are likely to be without Ben Roethlisberger. Seemingly nothing stands between New England and a divisional playoff date at Foxboro on the weekend of Jan. 15.

Which brings us to this:

Is this game with Miami causing anyone at least a little anxiety?

Don't look now, folks, but the Miami Dolphins are not the complete doormat on which the Patriots wiped their feet in a season-opening, 38-24 win. Miami quarterback Chad Henne passed for a whopping 416 yards in that game - the concerns about the Patriots defense this year have been there from the start - but the greater mismatch that night was between the Patriots offense and a Miami defense was supposed to be among the better units in the league.

Know what has happened since? During a season that began with an 0-7 start and led to the dismissal of head coach Tony Sparano, Miami has begun playing like far more people expected, steadily improving to the point where the Dolphins now have allowed fewer points per game (on average) than all but four teams in the league.

Let's say that again.

For the season, Miami ranks No. 5 in the league in scoring defense. And since Nov. 1, Miami's average of 14.1 points allowed per game ranks behind only the San Francisco 49ers and Pittsburgh Steelers in all of football.

Admittedly, with the Patriots, defense has been a far greater problem and concern this year, which makes the Miami game worth watching on multiple levels. Buoyed by the brilliance of Tom Brady - QB12 has 15 touchdown passes and just one interception in his last six games - the Patriots have been able to make up for any and all defensive deficiencies. The Patriots now have scored 30 or more points in 19 of their last 22 regular season; in those contents, they are a sterling 18-1 (the only loss came at Buffalo this year).

By contrast, in the other three games - all played this season - the Patriots are 1-2. They lost at Pittsburgh. They lost to the New York Giants. Their only victory came against the Dallas Cowboys, an affair in which Cowboys head coach Jason Garrett foolishly put the ball back in Brady's hands with 2:31 play.

All of this brings us back to the Dolphins, who will be the last above-average defense New England will face until the postseason.

Here's the point: when factoring in New England's last three playoff losses with its three toughest games this year - the Steelers, Cowboys and Giants - the formula for beating New England seems clear. The Patriots rarely win a game with their defense, plain and simple, which suggests that any and all discussion about the Patriots' Super Bowl chances should not focus solely on the New England defense.

It should focus on the opposing defense, too.

As such, here's the question we all have to ask ourselves as the Patriots approach the end of the regular season and the start of the playoffs: what do you believe in? Do you believe New England can win with offense, the way New Orleans did in 2009? Or do you believe in at least some representative measure of defense, as most traditionalists would argue? Of the four participants in last year's conference championship games, all four ranked among the top six in the NFL in scoring defense. A year earlier, Super Bowl participants Indianapolis and New Orleans ranked a respective eighth and 20th.

Last year, when the Patriots lost to the Jets in the divisional round, much was made of the underperformance of the New England offense despite the fact that the Jets had one of the best defenses in the league. Does that make any sense at all? A year prior, Baltimore's strength was similarly its defense. And yet, everyone reacted with surprise when the Ravens battered Brady and rolled to a 31-14 win.

The reason we all did that, perhaps, is because we knew the Patriots did not have a championship-caliber defense. Presumably, we all know the same now. And so in that respect, the question becomes not whether New England can stop anyone at a critical juncture - they can't - but whether the Patriots can score enough to keep their defense out of critical situations.

The Dolphins, of course, will not be participating in the postseason this year. But in the modern NFL, their defense qualifies as well above average, which presents a good challenge for the Patriots this week. Unlike Week 17 opponent Buffalo, which ranks 27th in the league in scoring defense, the Dolphins of today (unlike the Miami team of Week 1) should present at least some challenge to a New England offense that has averaged 35.8 points per game, albeit against a succession of teams that currently rank 21st (the Jets), 22nd (Chiefs), 19th (Eagles), 30th (Colts), 16th (Redskins) and 24th (Broncos) in scoring defense.

What that tells us, it seems, is that the Patriots can shred a mediocre or poor defense.

What we still do not know, entering Miami, is whether the Patriots can shred a good one, at least well enough.