Halfway through the NFL season, and some of the longstanding football beliefs seem half-baked.
The past nine weeks have put some rules of thumb to the test, some because of surprising trends, others due to statistical curiosities.
Now that every team has at least eight games in the books, here are eight theories under heavy pressure.

Defense wins titles
That was certainly the case in the most recent Super Bowl, with Denver’s dominating defense roughing up Carolina’s top-ranked offense. But lately, some of the best defensive teams have been struggling. Check out the records in the last five games of the teams with the top five defenses: Arizona (2-2-1), Baltimore (1-4), Minnesota (2-3), Denver (2-3) and Houston (3-2).
Conversely, the top five offensive teams have been rolling over the same span: New Orleans (4-1), Atlanta (3-2), Dallas (5-0), Washington (3-1-1) and Oakland (4-1).

Beware of the rookie quarterbacks
The Cowboys have won seven in a row with rookie Dak Prescott at the helm. He has thrown for 12 touchdowns with two interceptions, and has run for four scores. Philadelphia rookie Carson Wentz has come back to earth after a 3-0 start, with the Eagles losing four of five.
In all, five rookie quarterbacks have started games this season, the others being Cleveland’s Cody Kessler, New England’s Jacoby Brissett and Denver’s Paxton Lynch. Seattle’s Trevone Boykin and Kevin Hogan of the Browns have also thrown passes in games. Seems like the only rookie quarterback who hasn’t played is No. 1 overall pick Jared Goff of the Rams.

Kickers getting too good
That’s why the league moved extra points back, right? Well, kicking miscues are a weekly occurrence this season. Second-round pick Roberto Aguayo has made every field goal an adventure in Tampa Bay. Arizona’s Chandler Catanzaro and Seattle’s Stephen Hauschka both made and missed field goals in overtime of a game that ended in an ugly 6-6 tie. And Pittsburgh’s Chris Boswell had the worst onside-kick attempt in memory Sunday, when he tried a nifty soccer move and barely knocked the ball off the tee.

TV ratings bulletproof
Ratings have plunged this season, causing significant concern within a league that unfailingly mints money. Theories abound for the swoon: viewers are preoccupied with the election; the concussion issue has hit home; too many game days (and not enough good games); and residual anger over players kneeling during the national anthem. Lots of questions, but no firm answers yet.

Penalties will kill you
They haven’t done in the 7-2 Raiders, who have a league-leading 94 flags – 23 more than Denver, which is second on that list. Does 23 sound familiar? Oakland was flagged an NFL-record 23 times at Tampa Bay in Week 8 ... and won.

You need to win the turnover battle
It sure helps. In fact, that’s typically the most telling statistic (aside from final score) when it comes to determining wins and losses. But there are some strange turnover differentials out there at the midway point. Buffalo (plus-eight), Philadelphia (plus-six) and New Orleans (plus-four) are near the top of the list but are a collective 12-13, with none having a winning record. The New York Giants and Houston are tied near the bottom at minus-seven, yet both are 5-3.