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The biggest task for any predictive model is to figure out which teams are "for real" before a general consensus catches on.  There will always be some noise in the tiny sample size of an NFL season, especially through six weeks, but at the very least, we are reaching the point when these rankings begin to stabilize.

Unlike the first two renditions of these rankings, there were no big ascents or collapses, with no team moving more than six spots from their Week 5 position.  Thus, it appears the model is moving closer towards answering that question posed in the first sentence.

Still, we are hardly capable of making sweeping conclusions based on that fact alone.  So this week's write-up will start with a dive into two top-10 teams, both of whom are also steadily gaining steam in the national media.

To Believe or Not to Believe?

Do these two teams really belong in the upper-third of the league?

- It almost feels reasonable to doubt the Cleveland Browns based solely on metaphysical reasons.  But whatever bad juju the Browns have accumulated since their 1999 reincarnation has disappeared in this felicitous campaign, as the 3-2 Browns sit eighth in this week's rankings.

It's not hard to identify where the Browns have thrived.  The Johnny Manziel Brian Hoyer-led offense ranks second in overall efficiency, with Hoyer spearheading the fifth-ranked passing game in terms of Expected Points Added (EPA) per play. 

That the Browns are doing this without All-World receiver is nothing short of remarkable.  Andrew Hawkins has received love among statheads, but the diminutive slot receiver is flanked by the brittle Miles Austin, punt returner Travis Benjamin and undrafted rookie Taylor Gabriel.  Even Pro Bowl tight end (er, pass catcher) Jordan Cameron has been hampered with a shoulder injury, accruing just nine receptions over four games thus far.

In truth, most of Cleveland's success stems from Hoyer's lack of turnovers.  Though he is middling in terms of success rate and EPA/P, Hoyer ranks third in adjusted yards per attempt (7.3), in part because he has been picked off twice and sacked just seven times. 

There are also some important misconceptions surrounding Hoyer.  Despite his reputation as a dink-and-dunker, 28 percent of Hoyer's passes have traveled at least 15 yards, the fourth-highest rate in the league.  Moreover, Hoyer is not getting by with a bunch of clutch fourth-quarter comebacks, as his total Win Probability Added (WPA) is almost exactly in line with what we would expect him to produce given his EPA:

Even if Hoyer's turnover rate regresses, the Browns can turn to a running game that currently boasts the seventh-best success rate in the league at 45 percent.  The rookie tandem of Terrance West and Isaiah Crowell excelled over the first month, raising questions as to whether Ben Tate deserves his starting spot back. 

Tate has averaged 4.7 yards per carry over his four-year career, but injuries and fumbilitis (10 fumbles in just 43 career games) have plagued the talented back.  In fact, AFA has seen Tate as a significant net negative over the past two years:

In fairness, Tate has posted a generally adequate success rate, as his 46.4 percent rate this season would rank eighth among backs with at least 50 carries.  Nevertheless, the West-Crowell tandem has helped Cleveland produce the third-highest rushing EPA/P this season.  Just as Hoyer's unexpected success has provided the Browns no reason to play the first-rounder Manziel, West and Crowell have suggested that the free-agent signing Tate should not immediately re-assume the majority of the carries.

There are certainly real problems with Cleveland that could derail their hot start.  You'll notice that not one peep has been made about their defense, which sits 26th in these rankings and 31st in Football Outsiders' DVOA.  Additionally, the loss of All-Pro center Alex Mack could be devastating, as right guard John Greco will now slide over into the middle, with Paul McQuistan filling in for Greco's old spot.  That's a potential downgrade at two interior positions, which likely has bad implications for the running game.

But with an upcoming three-game stretch against Jacksonville, Oakland and Tampa Bay, the Browns have an opportunity to bank six wins by midseason.  The freebies end there, as the Browns do not face a team in the second half that currently owns a losing record, apart from a Week 12 trip to the Georgia Dome. 

The Browns are a weird team because we can predict most of the important shifting variables that will come into play.  Does Gordon's return and Cameron's improving health offset the likely turnover correction from Hoyer?  Will Joe Haden begin to post numbers more commensurate with his play? How much does Mack's absence hurt the running game?  To date, Cleveland has fully earned its current top-10 status, but if the Browns are to make the playoffs for just the second time since their revival, the margin for error is smaller than their eighth-place ranking would suggest.

- The Detroit Lions have possessed top-tier talent for years now, and this not the first time they have teased.  In their 2011 playoff campaign, the Lions started 5-0, with a plus-70 point differential that was second-best in the league.  Last year, Detroit started 6-3 and were sat ninth in these very rankings at the time.

The difference this year is that the Lions are not merely a high-flying squad whose fortunes rest on Matthew Stafford's fickle right arm.  Detroit possesses the first-ranked defense by not only this site's rankings, but also multiple other metrics.  By all accounts, the Lions defense has stood out as far and away the best in the league:

Most jarringly, the Lions rank first in pass defense EPA/P, as they are the only team to hold opposing offenses to a negative EPA this season.  This is a team with Darius Slay and Rashean Mathis as its starting corners.  Isa Abdul-Quddus has received significant playing time at safety.  Injuries have wreaked havoc on the all-important nickel corner position, where the Lions are on their fourth option in Danny Gorrer.  Gorrer, who Detroit signed on September 16, has been in the league since 2009 and has been cut seven times.

I say these things not to overwhelm you with trivia on obscure defensive backs, but to highlight how absurdly mind-boggling it is that the Lions have been the best pass defense in the league with this secondary.  Some of this is due to the Lions' excellent front seven, of course, but no one posts a league-leading rate from pass-rushing alone.  Detroit does rank first in sack percentage, but eight of their 20 sacks came last week against the overwhelmed Vikings.

Still, it would be a discredit to simply gloss over the All-Pro performances put forth so far by Ndamukong Suh and DeAndre Levy, both of whom can make claims as the best players at their respective positions.  The latter in particular has stepped up for the loss of excellent middle linebacker Stephen Tulloch, posting the highest EPA per game of any linebacker in the league this season.  Levy's freakish athleticism has turned him into one of the game's best all-around linebackers, alongside Lavonte David and (when healthy) NaVorro Bowman.

As for that much ballyhooed offense, it appears new offensive coordinator Joe Lombardi has made a critical difference in Stafford's career.  Lombardi, who was Drew Brees' old quarterbacks coach, has transported the high-percentage West Coast principles from New Orleans to the Motor City.  Consequently, Stafford is on-pace to throw just 11 interceptions this season, which would be by far his lowest mark in a healthy season (he threw 17 in 16 games in 2012).

While Stafford's success rate has taken a small hit, he is also completing over 62 percent of his passes while posting a 0.20 WPA, both of which would be his best marks since 2011.  Injuries to Calvin Johnson, Reggie Bush, Joique Bell and Joseph Fauria have deflated Detroit's overall offensive stats.  Still, there is reason to believe those numbers will rebound once Stafford's skill position support returns to full health.

If there's a concern with the Lions, it is along the offensive line.  Detroit has surrendered 20 sacks this season, third-most in the league.  Those aren't isolated incidents either, as the Lions have also conceded 29 quarterback hits (fifth-most) and 21 tackles for loss (tied for fourth-most).

Right tackle had been a revolving door, with Garrett Reynolds and Cornelius Lucas splitting duties, but normal starter LaAdrian Waddle returned two weeks ago against Buffalo.  Veteran left guard Rob Sims has been the other troublesome starter, allowing a team-high 10 quarterback hurries, according to Pro Football Focus' count.

Even with the line's issues, though, Detroit is no longer a high-variance team vulnerable to wild weekly fluctuations.  Apart from a Week 2 clunker against Carolina, most of the Lions' games have looked remarkably similar.  If the likes of Mathis, Slay and Glover Quin in the secondary can continue pulling their weight to buttress the sterling front seven, Detroit's defense makes the Lions legitimate contenders, even in the deep NFC.

Biggest Movers

These teams experienced the biggest rise and fall from Week 5.

- The Niners rose seven spots up to fifth place, but we just extensively covered their future outlook last week.  We'll revisit San Francisco in a few weeks, but the 49ers figure to be one of five or six teams jostling for one of a few precious NFC playoff berths.

The Chicago Bears rose five spots, behind San Francisco and Cleveland (six spots) for the largest jump from Week 5.  Despite an important win at the Georgia Dome, the Bears look like a tricky team to pin down, in no small part because of Jay Cutler's week-to-week (or even quarter-to-quarter) inconsistencies. 

The narrative on Cutler is well-documented at this point: he's an uber-talented gunslinger with questions about mechanics, consistency and leadership, and thus a questionable leader for a team with Super Bowl aspirations.  This season, the numbers have leaned more towards good Cutler, as he ranks third in success rate and has posted the highest EPA/P of his Chicago tenure.

And yet, the Bears rank as exactly a league-average team in terms of pass efficiency.  The bottom line remains relatively unspectacular, despite Cutler on pace to post career-highs in Adjusted Net Yards per Attempt and completion percentage.  In examining Cutler's splits by half, we can see that that incongruency results from a bizarre trend:

Despite a higher completion percentage, Cutler is also somehow making more mistakes and thus harming Chicago down the stretch.  It's hard to go with the facile "not clutch" narrative, though, for every second-half stinker like Chicago's Week 4 loss to Green Bay, Cutler has catalyzed a brilliant finish, as he did in victories over San Francisco and Atlanta.

It's not particularly instructive to examine the rest of the team, either.  The Bears' defense has stabilized after demonstrating historically poor resistance against the run in 2013, but they still rate out as a roughly league-average unit whose positive impact stems from a 4.0 percent interception rate that ranks fourth-highest in the league.  Matt Forte is producing by far the highest success rate of his career at 46.2 percent.  Only Le'Veon Bell and DeMarco Murray have topped that mark while recording at least as many carries as Forte's 99.

Thus, the cumulative picture would seemingly portray a team that deserves a ranking higher than No. 18.  The formula is not impressed overall with Chicago's defense, ranking them 24th, but the Bears' have conceded just 0.08 EPA/P, which ranks eighth in the league.  Just one of Chicago's six opponents currently rank in the top-10 in terms of overall efficiency, so a low opponent gross winning percentage (GWP) is probably dragging the Bears down.  Nonetheless, it is clear that the addition of impactful rookies (Kyle Fuller, Ego Ferguson) and veteran free agents (Lamarr Houston, Willie Young) will prevent the defense from dragging the Bears out of the playoffs, as they essentially did in 2013.

One solution to Chicago's late-game inconsistencies could simply be to take the ball out of Cutler's hands more often.  The Bears run the ball on just 37.5 percent of their plays, 26th in the league and the lowest of any team with a .500 record or better.  That number has shimmied up to 39 percent in the second half, but that still feels low for a team that has run the fourth-most offensive plays in one-possession second-half situations.

The Bears might be the league's toughest team to grasp at the moment.  The Packers will always have staying power with Aaron Rodgers, and we've already outlined the reasons for Detroit's legitimacy.  Chicago clearly possesses playoff-caliber talent, but as in years past, the numbers just do not seems to add up in their favor.

- On the other end of the spectrum, the New York Giants fell six spots to 22nd overall, tied with the Chargers for the largest drop.  In a surprisingly competent NFC East where the Cowboys and Eagles are 5-1, the G-Men might look like the clear third wheel at the moment.

However, Pro Football Reference's Pythagorean Win Expectancy pegs Dallas, Philly and New York at 3.9, 4.1 and 2.9, respectively.  In other words, PFF sees the Giants as having performed almost exactly to expectations thus far, while the Eagles and Cowboys have both overachieved by a win.

That observation about Philly and Dallas likely does not surprise anyone who has followed either team this season, but the Giants have been a much more erratic bunch whose dizzying week-to-week sways ultimately leave them somewhere in the middle. 

Then again, the Giants might be an easy team to decipher.  For the most part, their EPA has correlated almost entirely with opponent strength.  This holds particularly true for the much-ballyhooed new Ben McAdoo offense, which has alternately been hopeless and unstoppable:

Again, though, it seems too simplistic to suggest that the entire offense simply fluctuates based on opponent strength.  Dissecting things deeper, the Giants have bizarrely received season-best outliers in each of their three victories—Rashad Jennings vs. Houston, Larry Donnell vs. Washington and Odell Beckham, Jr. vs. Atlanta.  Calling Beckham's performance an outlier might be a reach, since he is a rookie who has played just two games, but it doesn't seem like a stretch to suggest that the Giants' 23rd-ranked offensive efficiency would sit even lower if not for those one-time leaps in performance.

With Victor Cruz done for the year, the Giants will probably need to rely on their talented yet inconsistent defense to win them games.  New York stands out as the best run defense in terms of success rate, with Jason Pierre-Paul in particular rebounding from a lost injury-plagued 2013 campaign to restore his status as one of the game's top young defensive ends. 

But the secondary, the team's ostensible preseason strength, has fallen well short of expectations.  A season-ending pectoral injury to excellent slot corner Walter Thurmond hasn't helped, while Stevie Brown has regressed mightily, to the point of being benched for Quintin Demps.  Dominique Rodgers-Cromartie has also been in and out of the lineup with nagging injuries, though Prince Amukamura's breakthrough has helped offset DRC's absence.

Either way, we'll get a much better idea of if the Giants defense can carry the Cruz-less offense.  Four of New York's next five opponents currently rank in the top 10 in overall offensive efficiency.  The 49ers are the one exception, but they rank 10th in passing efficiency.  The Giants have gotten by against a relatively weak schedule with a few spectacular performances, but Cruz's injury is a reminder that they will need to establish a more permanent foundation to keep up with Dallas and Philadelphia.

Pooch Punts

- Like the Bears, the Philadelphia Eagles also rose five spots in the standings.  Because these rankings don't account for Philly's wildly successful special teams unit, it's hardly a surprise that the Eagles still rank just 24th after several slipshod efforts that resulted in wins anyways.

LeSean McCoy's inevitable rebound (tied largely to offensive line health) began last week, while questions about Nick Foles' mechanics persist.  As fun as the Chip Kelly-engineered offense is to watch, however, the more intriguing unit may be Philly's 10th-ranked defense.  The Eagles grade out as only slightly above-average in both run and pass defense, but as we can see, things have not exactly gone smoothly:

Much of that stems from the inconsistent cornerback play, as the likes of Cary Williams and Bradley Fletcher have committed some head-scratching errors this season.  But the Eagles have boosted their 31st-ranked sack percentage all the way up the seventh this season, while also receiving steady support from veterans Malcolm Jenkins, DeMeco Ryans and Connor Barwin.  If the #FreeBrandonGraham movement ever reached Eagles headquarters, that sack rate might shoot up even higher.

The Eagles face four division games in their final five contests, with a daunting road trip to Seattle sandwiched in between.  So while Philly's stock figures to rise over the next six weeks, they will likely remain a tricky postseason proposition until the final month.

- The Denver Broncos are the new number one team in the rankings, eeking past the sister-kissing Bengals.  This looks like a deserved change, for while Cincy looked like the league's most complete team over the first two weeks, defensive debacles against New England and Carolina raise enough questions about the Bengals (even while ignoring their recent past).

In spite of a poor running game, the Broncos have surged to the top behind more than just Peyton Manning's immaculate right arm.  Denver is currently just one of three teams to sit in the top 10 of both run and pass defense success rate, along with the Giants and Dolphins.  The Broncos rank first in the latter category, the result of a premier edge-rushing duo in Von Miller and DeMarcus Ware supporting a secondary with three Pro Bowl-caliber starters in Aqib Talib, T.J. Ward and Chris Harris, Jr.

The offensive line has had peculiar issues run-blocking, whether for Montee Ball or Ronnie Hillman, but a below-average ground game is not going to hold back an elite defense and passing attack.  In a season where no team looks particularly dominant, the Broncos stand out as a potential candidate to fill that void.

Here are the updated team efficiency rankings after six weeks.  As always, observations, questions and snide remarks are welcome in the comments section.

1 DEN 3 0.62 0.50 7 3
2 CIN 1 0.62 0.50 1 6
3 SEA 2 0.59 0.56 8 12
4 MIA 5 0.58 0.49 19 2
5 SF 12 0.57 0.48 13 4
6 DAL 9 0.56 0.51 5 21
7 DET 7 0.56 0.48 22 1
8 CLE 14 0.55 0.51 2 25
9 GB 6 0.55 0.52 18 5
10 SD 4 0.55 0.45 4 9
11 BAL 10 0.54 0.51 12 20
12 WAS 8 0.52 0.47 6 15
13 NO 11 0.52 0.46 3 28
14 KC 17 0.51 0.56 25 17
15 IND 13 0.51 0.50 9 22
16 NE 19 0.51 0.50 16 7
17 CAR 21 0.51 0.51 21 8
18 CHI 23 0.51 0.49 11 23
19 TEN 15 0.51 0.52 20 19
20 PIT 18 0.49 0.48 14 18
21 HOU 22 0.48 0.49 15 26
22 NYG 16 0.47 0.48 23 16
23 BUF 20 0.46 0.53 27 11
24 PHI 29 0.46 0.48 24 10
25 NYJ 26 0.45 0.53 31 13
26 ARI 25 0.43 0.54 28 24
27 MIN 27 0.43 0.49 30 14
28 ATL 24 0.41 0.48 10 32
29 OAK 30 0.40 0.51 26 29
30 STL 28 0.40 0.47 17 30
31 JAC 31 0.39 0.51 32 27
32 TB 32 0.35 0.48 29 31

ATL 7.4 38 3.4 1.4 8.0 55 1.0 0.49
ARI 5.9 30 0.0 1.6 7.6 67 4.1 0.40
BAL 6.8 42 1.4 1.1 6.8 64 1.8 0.31
BUF 6.0 35 2.3 1.8 6.6 66 2.6 0.61
CHI 6.5 47 2.6 1.9 6.9 58 4.0 0.49
CAR 6.5 36 0.9 2.0 6.4 63 3.1 0.45
CIN 8.3 40 1.9 0.9 5.6 48 3.2 0.44
CLE 7.5 45 0.7 1.3 6.7 52 2.2 0.47
DAL 7.1 47 2.6 2.8 6.7 57 3.6 0.36
DEN 7.6 37 1.6 1.3 5.4 64 1.9 0.50
DET 6.2 40 1.9 1.8 5.2 62 3.4 0.39
GB 6.4 40 1.0 1.5 5.8 49 4.4 0.35
HOU 7.3 37 3.7 2.4 6.6 49 2.5 0.47
IND 7.2 40 2.7 1.3 6.7 56 3.1 0.48
JAC 5.3 36 3.6 1.5 7.2 63 0.4 0.27
KC 5.8 40 2.5 1.8 6.2 54 1.3 0.28
MIA 5.5 53 2.7 2.4 5.4 64 1.6 0.25
MIN 5.2 43 4.5 0.9 6.3 60 2.6 0.47
NE 6.2 43 0.9 1.8 6.0 54 3.6 0.68
NO 6.9 52 2.8 1.1 7.4 63 0.6 0.25
NYG 6.1 41 2.5 2.2 7.2 69 4.8 0.36
NYJ 4.8 45 3.3 2.7 6.2 64 0.5 0.52
OAK 5.9 39 3.8 1.6 7.3 55 1.3 0.41
PHI 6.4 34 2.9 1.9 6.1 60 1.3 0.41
PIT 6.5 44 1.4 1.5 6.6 61 1.5 0.63
SD 8.2 31 1.0 1.5 5.8 52 2.0 0.45
SF 6.9 41 2.1 1.0 5.5 61 3.2 0.56
SEA 6.2 51 1.4 2.4 6.5 68 1.1 0.49
STL 6.3 44 2.5 2.7 7.7 61 2.1 0.67
TB 5.8 36 3.3 2.5 7.8 62 1.8 0.47
TEN 6.4 42 3.2 1.8 6.5 54 3.3 0.55
WAS 7.4 42 3.5 1.7 6.3 64 1.0 0.63
Avg 6.5 41 2.4 1.7 6.5 59 2.4 0.46