Our weekly attempt to expose and explore the gray area involved in officiating NFL games. Sunday suggestions welcome via Twitter (@SeifertESPN).

Play: No flag for a helmet-to-helmet hit by Chicago Bears safety Ryan Mundy on Atlanta Falcons receiver Roddy White

Referee: Walt Anderson

Analysis: As Matt Ryan's pass approached White, Mundy took a textbook 2014 approach, initiating contact with his right shoulder and first striking White's left shoulder. At live speed, however, White's head snapped back -- a tell-tale action that routinely draws flags against modern NFL defenders.

Ryan Mundy wasn't penalized for this hit Sunday on Roddy White. Todd Kirkland/Icon Sportswire

The assumption is that helmet-to-helmet contact causes a head-snap. On cue, Anderson's crew dropped a late flag. But after discussion, Anderson waved it off and said there was no foul because the "contact was with the shoulder."

Watching the play in slow motion revealed that, after the shoulder contact, the crown of Mundy's head struck the lower left side of White's helmet. White qualified for defenseless player protection under NFL rules -- "a receiver attempting to catch a pass" -- and Rule 12, Section 2, Article 7(b) prohibits "forcibly hitting [the] head or neck area with the helmet, facemask, forearm or shoulder even if the initial contact is lower than the player's neck."

A note added to that rule states it "does not prohibit incidental contact by the mask or helmet in the course of a conventional tackle."

The past few years have conditioned us to expect a penalty on this kind of hit, even though it was once a standard part of legal defensive play. White was defenseless, Mundy made at least some contact with the helmet and White was slow to get up.

But was the contact "incidental?" Former NFL vice president of officiating, Mike Pereira, thought it was and indicated as such on the Fox broadcast. Former NFL referee Jim Daopoulos, on the other hand, tweeted that the hit "is a foul and the flag should not have been picked up."

Anderson's explanation indicated he hadn't seen any helmet-to-helmet contact, so it's difficult to know whether he considered the "incidental" exception. Based on the rules cited, you can make an argument for "incidental" contact even if it wasn't at the root of Anderson's decision. Still, Mundy and the Bears should consider themselves fortunate. These days, any contact forceful enough to cause a head-snap usually leads to a penalty.

Offsetting penalties overturn a Minnesota Vikings turnover against the Detroit Lions

Referee: John Parry

Analysis: Vikings punt returner Marcus Sherels fumbled after a 14-yard return in the second quarter. The ball was recovered by the Lions' Tahir Whitehead.

After the play, Parry's crew sorted through three separate penalties. Two were on the Vikings: holding by Shaun Prater and an illegal block on a player Parry announced as No. 47. (There is no 47 on the Vikings' roster.) In addition, the Lions' Julian Stanford was called for illegal use of hands.

The NFL rule book has an entire section devoted to offsetting penalties on a change of possession. The end result was a replay of the down, even though the Vikings had committed two of the three penalties and the Lions had recovered Sherels' fumble.

Why the inequity? The two-word answer is "clean hands."

Here is what Rule 14, Section 5, Article 2 says about a double foul with a change of possession: "[T]he team last gaining possession will keep the ball after enforcement for its foul, provided it did not foul prior to gaining possession ('clean hands'). If the team last in possession does not have "clean hands" when it establishes possession, the penalties offset, and the down is replayed on the previous spot."

In other words, the Lions didn't keep the ball because Stanford committed his penalty before Whitehead recovered the fumble. The Lions didn't have "clean hands" prior to gaining possession, and it was irrelevant to this rule that the Vikings had committed two penalties to the Lions' one. Here's hoping for better hygiene next time.

Unsportsmanlike conduct on Buffalo Bills defensive end Jerry Hughes for … what?

Referee: Walt Coleman

Analysis: In the first quarter, the Bills' defense stopped New England Patriots running back Stevan Ridley for no gain on third-and-1. Hughes celebrated with teammates, at one point reaching over the pile to slap teammate Ty Powell's helmet as Ridley rose from the ground.

Coleman called Hughes for unsportsmanlike conduct, with no further explanation, to give the Patriots a first down. (The extended possession did not result in points.) Why would a player be penalized for hitting his own teammate's helmet? There are a few possibilities, although none are immediately apparent when watching the replay.

Rule 12, Section 3, Article 1(b) prohibits "using abusive, threatening or insulting languages or gestures to opponents, teammates, officials or representatives of the league." Did Hughes use a word or phrase toward Powell that Coleman's crew interpreted as "abusive, threatening or insulting?" In addition, Article 1(c) prohibits "using baiting or taunting acts or word that engender ill will between teams." Hughes' helmet blocks any visual view of whether he was saying anything, let alone something that qualifies here.

Meanwhile, Article 1(d) prohibits "prolonged or excessive celebrations or demonstrations," defined as a player continuing "to celebrate after a warning from an official." If Hughes was warned for what seemed to be a short-lived celebration, it's not visible on the replay.

Ridley had to redirect himself slightly to get around Hughes' arms as he rose from the ground. Was that enough to qualify as an "abusive" gesture? I would think not. Nor should it qualify under Article 1(a), which prohibits "throwing a punch, or a forearm, or kicking at an opponent, even though no contact is made."

Absent a more specific ruling from the NFL, the likeliest explanation: Coleman's crew thought Hughes either smacked Ridley's helmet or was trying to. Otherwise, the call is difficult to explain.