Ryan Clark explains why the Patriots' defense, as it's currently playing, will prevent New England from repeating as Super Bowl champions. (0:43)

The New England Patriots' defense gave up 42 points and more than 500 yards to the Kansas City Chiefs to open the season. The Patriots rebounded with a win over the New Orleans Saints in Week 2, but still allowed the Saints to gain 429 yards.

There was some explanation for this. The Chiefs and Saints are among the NFL's best offenses, and the Patriots gave up some of those yards to New Orleans in garbage time. It wasn't absurd to think that the New England defense would overcome the struggles of the first two weeks and right the ship.

But then, in Week 3, they again gave up more than 400 yards and needed a last-minute touchdown pass from Tom Brady to beat a Houston team with a rookie quarterback. Unlike the Chiefs and Saints, the Texans are definitely not among the NFL's best offenses.

New England is last in the NFL in almost every defensive statistic. In Football Outsiders' DVOA ratings, the gap between the No. 32 Patriots and the No. 31 Saints is larger than the gap between the Saints and the No. 21 Cleveland Browns.

Can the Patriots possibly win the Super Bowl with a defense this bad?

The simple answer is "no." Here's where the Patriots stand through three weeks compared with the worst defense in the correlating stats to ever win (or appear) in a Super Bowl:

Worst SB Winner Worst SB Team 2017 Patriots Pts/game 2011 Giants, 25.0 (25) 2008 Cardinals, 26.6 (28) 31.7 (32) Yds/play 2011 Giants, 5.61 (22) 2011 Patriots, 6.18 (30) 7.09 (32) Sack rate 2016 Patriots, 5.4% (18) 2016 Falcons, 4.9% (26) 5.0% (26) DVOA 2006 Colts, 8.5% (25) 2011 Patriots, 13.2% (30) 35.4% (32) Rank for season in parentheses.

New England fans are familiar with a lot of these teams. Six years ago, they watched another Patriots team with a terrible defense reach Super Bowl XLVI, where they lost to the Giants, thanks to a stellar offense. But you'll notice that all the teams that made the Super Bowl despite bad defenses were still much better on D than the Patriots have been so far. There's no way New England can be a Super Bowl contender if its defense continues playing this poorly.

The good news for Patriots fans is: That is very unlikely. It's easy to see that when you compare the Patriots to similar teams of the past.

To start, we looked through the past 20 years for other teams that were very poor on defense through the first three games, but still had a winning record. Sixteen teams over the past 20 years had a winning record after three games despite ranking among the five worst teams in defensive DVOA. Twelve of those 16 teams ended up making the postseason, although only one -- the 2006 Colts -- won the Super Bowl.

Of course, this isn't necessarily the best crop of teams to measure the 2017 Patriots against because they have been so bad early on; only two of the 16 teams were worse than the 2017 Patriots have been through three weeks. The Bengals' defense in 2012 eventually improved to 10th in DVOA, and the team ended up as a 10-6 wild card. The 2010 Texans were terrible on defense all season, finishing 31st in DVOA with a 6-10 record.

Yet, while most of these "bad early defense" teams were not as bad as the Patriots have been this year, there's encouragement for New England fans. Three other Patriots teams are on that list of 16. The 2006 Patriots, who finished the year seventh in defensive DVOA, show that a terrible start doesn't necessarily mean terrible defense all year, while the 2010 Patriots (21st) and 2011 Patriots (30th) are proof that you can overcome poor defense and still make the playoffs with a powerful offense.

Close to the 2017 Patriots, you'll find the team that was last in defensive DVOA after three games last year: the Atlanta Falcons. The Falcons started 2016 with three shootouts and went 2-1. Like the Patriots, the Falcons' defense looked bad early in part because they had to play New Orleans and a high-powered AFC West offense, the Oakland Raiders.

Kansas City rookie running back Kareem Hunt gashed the New England defense for 246 yards from scrimmage and three total touchdowns in the season opener in Foxborough. Maddie Meyer/Getty Images

However, the Falcons' defense finished the year better than it started. That could be what's in store for the Patriots this year: a defense that isn't quite as good as people expected before the season, but still a lot better than it has been through the first three weeks. By the end of last season, Atlanta had improved from 32nd to 22nd in defensive DVOA. Combined with the top offense in the league, that was enough for the Falcons to go 11-5 and win the NFC South. The defense played its best football in the postseason -- or at least the first 156 minutes of the postseason, and you know the rest of the story.

Another way to determine what could be in store for the Patriots is to look at the defenses of the teams that started 1-2 or 0-3. How much rebound was there from defenses that were middle of the road, like last year's Patriots, and then started the next season horribly? Although the Patriots ranked No. 1 in points allowed last season, they were only 16th in defensive DVOA for a variety of reasons. (The two most important: They had by far the easiest schedule of opposing offenses, and great special teams that consistently gave their defense long fields to defend.)

Twelve teams over the past 20 years started the first three games with defensive DVOA of 25.0 percent or worse just a year after they ranked between 10th and 20th on defense. By the end of the year, these teams on average ranked 23rd on defense. As with the comparison to the 2016 Falcons, this is not what Patriots fans wanted from a defense that was supposed to take a step forward in 2017, but it's a lot better than last.

There's a difference, of course, between asking "Can this defense win the Super Bowl?" and "Will this defense win the Super Bowl?" Only two Super Bowl champions since 1986 ranked 20th or worse in defensive DVOA during the regular season: the 1998 Broncos (20th) and the 2006 Colts (25th). Four other such teams made it to the big game and lost, all in very close games: the 1999 Titans, 2008 Cardinals, 2011 Patriots and 2016 Falcons. A handful of Super Bowl champions have had defensive DVOA slightly worse than average, but ranked in the teens, including the 1993 and 1995 Cowboys, 2011 Giants and 2012 Ravens.

All those teams fall into two categories. There are the "surprise" teams that went on unexpected postseason runs: the 2008 Cardinals, 2011 Giants and 2012 Ravens. Then there are the teams that had powerful offenses that were near the top of the league. The 1995 Cowboys, 1998 Broncos, 2006 Colts and 2016 Falcons all led the league in offensive DVOA. The 1999 Titans and 2011 Patriots ranked third.

There's a three-part answer to whether the Patriots can win the Super Bowl with this defense:

1. Sure, because any team that makes the playoffs can win the Super Bowl, but it would be a real long shot;

2. Their odds will be better if the defense improves, which it probably will;

3. But it's unlikely the defense will be any better than average for the rest of the year, which means the Patriots will need to have a top-three offense to be a serious Super Bowl contender.

Bottom line: They're no longer the prohibitive Super Bowl favorites they looked to be before the season began.